Laelaps aquilunguis, Cope, 1866

Cope, E. D., 1869, Synopsis of the extinct Batrachia, Reptilia and Aves of North America, Transactions of the American Philosophical Society 11, pp. 1-252 : 100-118

LAELAPS AQUILUNGUIS , Cope.

Loc. Cit. Leidy. l. c. 1868 .

This species was described by the author from a number of bones and fragments derived from the top of tl.e “chocolate" stratum of Cook & Smock’s upper bed of the Cretaceous Greensand of New Jersey, at a depth of about twenty feet below the surface. They were found by the workmen under direction of J. C. Voorhees, Superintendent of the Wrest Jersey Marl Company’s pits, about two miles south of Barnesboro, Gloucester co., N. J. The bones preserved were portions of the under jaw with teeth, portions of the scapular arch, including supposed pubes two humeri, left femur, tibia and fibula, with numerous phalanges, lumbar sacral and caudal vertebrae, and numerous other elements in a fragmentary condition.

The discovery of this animal filled a hiatus in the Cretaceous Fauna, revealing the carnivorous enemy of the great Herbivorous Hadrosaurus, as the Aublysodon was related to the Trachodon of the Nebraska beds, and the Megalosaurus to the Iguanodon of the European Wealden and Oolite.

In size this creature equalled the Megalosaurus bucklandii , and with it and Aublysodon , constituted the most formidable type of rapacious terrestrial vertebrata of which we have any knowledge. In its dentition and huge prehensile claws it resembled Megalosaurus . The species is now rediscribed with additional observations and with figures.

? Zygomatic arch.— A portion 6.5 inches in length is perhaps the malar portion of the arch rather than the squamosal, since near the termination of its inner or concave face it is pierced by a large foramen, similar in position to the suborbital foramen. The bone is slender, chiefly strengthened by a strong external, horizontal ridge, which is probably the homologue of that noticed by Prof. Owen as dividing the face of the maxillary and malar in Scelidosaurus. Alone and below this rib, the bone rapidly thins away. There is little curvature, indicating a long slender zygoma perhaps as in Compsognathus . The foramen has not been closed above.

	Lines.
Vertical depth inside of front of foramen,	18
Horizontal depth zygoma,	15

Maxillary bone.— A portion of the right maxillary displays parts of four alveolae: three of these have a flattened oval section, while the anterior is round, suggesting the presence of a canine-like tooth. One successional tooth in place extends from the bottom of the alveolus to within.75 inch of the maxillary border; it stands obliquely in place the posterior cutting edge being directed outwards. The anterior alveolus is shallower than the second, and this shallower than the third, which gives an oblique slope to the fractured margin of the bone, and suggests the application of another skeletal piece. This I suppose to be the premaxillary, as the bone is externally too flat to permit the median premaxillary suture to occupy that position. The upper portion may be related to the margin of the nares. A series of five foramina extends along the outer face of the bone opposite the middle of the depth of the alveolae. The alveolae are directed more anteriorly from behind forwards.

,

	Lines.
Depth of alveolus,	34
Length crown of successional tooth,	25
Length piece embracing four alveolae,	61

Mandible. — One portion from the anterior part of the ramus. The latter measure three inches in depth from the outer alveolar border, which is a little more elevated than the internal, and 1.5 in. in thickness at the fractured edge. A longitudinal series of vascular foramina extends along the middle of the external face. The teeth are implanted in deep alveolae, and had transversely oval compressed fangs; the sections of the crowns of teeth from different portions of the ramus differ. Two from the anterior region are considerably recurved, the concave or posterior edge deticulate to the base of the enamel, the anterior aspect minutely serrate, two fifths the length from the tip. Section at this point lenticular, lower down the anterior face becomes broader and rounded, giving a rounded cuneiform section. Throughout, one face is more convex than the other. A young posterior tooth yet in the alveolus (no. 3) is less recurved, subacute, and of more lenticular section, having both edges denticulate to the base of the enamel. Fangs hollow, the pulp cavity capacious but rapidly diminishing and short; the cast sulphide of iron and marl.

	Inches.
No. 1; total length (fang broken),	2.33
length of enamel,	1.83
width below,	.833
anterior diameter,	.438
No. 2; length of crown (tip restored),	1.875
anterior diameter,	.5
No. 3; length of crown,	2.125
width at base,	.688

Larger teeth are indicated by fragments. The development of the teeth has apparently proceeded as in Megalosaurus. The development of the dental papilla takes place within a niche of the alveolus, between it and the inner mandibular or maxillary wall. Small serate casps are found irx this position beneath but a thin stratum of bone. In one situation a second successional tooth occupies a position between the primary cusp and the functional tooth, and is about intermediate in size between them. These successional teeth then increasing in size, by a horizontal movement, transverse to the cranial axis, place themselves close to the fangs of the functional teeth, into whose places they gradually rise. An absorption of the dental wall probably prepares the older tooth for shedding, at which time the apex of the successional tooth is ready for use.*

Vertebra.— No cervical or dorsal vertebra were preserved; we have only as yet sacrals, and numerous caudals. All are much constricted medially, or hour-glass shaped, the centrum cylindrical in section throughout in most of the caudals, the anterior of the latter and the lumbars of deeper vertical than transverse diameter throughout. The articular surfaces are moderately shallow biconcave in all, most strongly in the subproximial caudals. The neural arches attached by permanent suture, and inferior surfaces for articulation of chevron bones. The caudals offer indication of neural spines; their traces are on the majority low, and of considerable longitudinal extent. Articular surfaces for chevron bones were much narrowed anterior to the middle of series, so that we can infer that the tail was proximally cylindrical. Zygapophyses turned upward, not outward.

The portions of the three sacrals preserved indicate that the centrum is very much compressed, as in other Dinosauria . The proximal caudals, or those with diapophyses, have also compressed centra, though this is less marked than in the sacrals. The diapophyses come off from the neural arch above its union with the centrum in four such vertebrae preserved. In these the arch is not coössified. In the remaining nine there is no trace of diapophysis beyond a ridge visible in the anterior ones, and the arches are codssified. In the four anterior there is on the posterior half of the median line below, a strong groove; in the two median, a foramen penetrates the centrum; in the posterior the groove is less posterior in its position. In the posterior series of ten it is represented by an indistinct plane. These vertebrae are relatively less compressed than the first, but have a more concave inferior outline. The neural spines of these have been apparently curved upwards and backwards, judging from the direction of the lines of ossific growth, as in Poecilopleurum . They originate a little anterior to the middle of the length of the vertebra. Anterior to this point the neural canal is only partially roofed over, there being an opening into it just in front of the base of the neural arch. Anteriorly the roof would appear to be composed by the union of two horizontal lamina1 of the anterior zygapophyses. The articular faces for chevron bones are small.

	In.	Lin.
Dimensions of an anterior caudal; length centrum,	4.	3
depth do. from suture of neural arch,	4.1	0
width articular face (anterior),	3.	6
" centrum at middle,	2.56	0
Length of median caudal,	4. 625
Breadth centrum,	2.375
Length base neural spine,	3.25
Length of a distal caudal (with neural canal),	2.875
Diameter centrum transverse,	1.125
“ “ vertical,	.875
Proximal caudal (with short diapophysis) length,	4.5
Depth centrum,	3.125
Width "	3.

Three separate vertebrae appear to be most probably sacrals, and indicate that this individual was not adult. Their form is much compressed, and the articular surfaces are rather expanded and concave. The superficial layer of the latter is very thin, and covered with delicate raised striae, mostly transverse in direction. They present the appearance of incomplete development, and would no doubt at a later period coössify with those of the adjacent vertebrae, forming the long sacrum common to the order. Their exterior dense walls are remarkably thin, and the internal structure of the centra is coarsely spongy or almost cavernous, being far less close and compact than that of the cancellous centra of the caudals. The largest of these has a strong median groove above, probably that of the neural canal: greatest elevation of articular surface 5 in. 2 lin., greatest width of same 4 in. 2 lin. The tissue of this centrum is so coarse as to resemble the borings of Teredo. In another a large foramen marks the mouth of a canal which enters the centrum just behind one of the articular surfaces, and above the thickest portion of the centrum. It descends obliquely towards the middle of the centrum, but its course can be traced only an inch. Foramen.9 inch in diameter.

The number of caudals preserved is fourteen. From interruptions in the series I imagine that ten have been lost, probably a few more; I think the whole number can be estimated at twenty-five. Both distals and proximals are preserved; the former are small and slender, the latter compressed, similar to the sacrals, and with diapophysis, and neural arch not coössified.

This furnishes a remarkable contrast to Hadrosaurus, to which Leidy reckons fifty- vertebrae, and a depth of tail of a foot and a half.

In comparing this series with those of Poecilopleurnm, so well illustrated by Deslongchamps, it is observable that vertebrae of similar proportions in the two are without diapophyses in the former, while they possess them in the latter. Thus the diapophyses probably cease at a point in Laelaps anterior to the same in Poecilopleurum . It is also noticeable that while they are obliquely directed backwards in the latter, those having them as well developed in the former exhibit them transverse.

Humerus.— Both are preserved, but lack the distal condyle; about half the coronoid fossa of one remains, furnishing an indication of the breadth of that extremity. They are proximally much dilated, having a very strong posteroexternal ala and a shorter antero-internal dilatation. They are not half the length of the femur; the shaft is flattened antero-internally. Of the proximal articulating surface a portion is lost, but a narrow surface continuous with it externally does not extend further out on the dilatation than opposite to the middle of the shaft. I find no trace of a globular condyle, as is seen in Hadrosaurus. Coronoid fossa large and well marked, not near to penetrating; medullary cavity of shaft relatively smaller than in the bones of the leg.

	In,
Length of humerus (restored),	12.
Greatest proximal breadth,	3.75
Distal breadth across coronoid fossa,	3.
Circumference of shaft,	5.3/8

These humeri are relatively shorter than in Hadrosaurus and Iguanodon, and the external alae do not pass so abruptly into the shaft as in them. They resemble most those of Poecilopleurum . They differ from these in being much dilated distally, especially internally, and in having the coronoid fossa much more pronounced.

Fore-limb.— In the lack of the necessary pieces, one cannot go far wrong in estimating the length after that of Poecilopleurum . In it the lower arm is three-fifths the humerus, which gives for Laelaps a length of 19.2 in. to the wrist. If we accept the Crocodile as the next nearest ally in the forelimbs, we find the carpus and hand to be.75 of the humerus. The ungueal phalange preserved in Poecilopleurum is shorter than in the Crocodile; if however we add 9 inches to the length already estimated, we have for the whole 2 ft. 4.2 inches.

This is, as will be hereafter shown, a little more than one fourth (1-3.71) the length of the hind limb.

Left Femur.— The head and summit of the great trochanter, and the posterior portions of the condyles, are broken away. The shaft is rather slender, and is strongly arched forwards and slightly outwards. The third trochanter is on the posterior face, is turned inwards, and marks one-third the length of the shaft from the supposed position of the head. Just below it the shaft is cyclo-trigonal, while for a short distance above the condyles it is flattened anteroposteriorly. It is strongly concave between the condyloid ridges at the distal end. At this place the external face is convex, the internal concave as high as a point a little more than a fourth the total length. The concavity is separated from the anterior face by a strong ridge which is partly broken away. The anterior surface is turned posteriorly to the external condyle, while it is concave and turned forwards to the internal condyle.

The posterior portions of the two condyles are broken away, so as to give their remaining portions almost exactly the form of the head of the femur in Hadrosaurus and Iguanodon. The dense layer of the remaining portions is much worn away, but enough remains to show that the external was rather the more prominent. The trochlear and popliteal concavities approach much nearer together than in Megalosaurus, causing a greater attenuation of the basis for the condyles. It cannot be ascertained whether the external condyle bore the small process behind seen in Megalosaurus ,

The neck is much compressed anteroposteriorly, and extends much interior to the line of the shaft. The posterior face is regularly convex, and then turns into the transversely convex exterior, which is divided above by the groove that separates the external trochanter. The broad posterior face narrows below this trochanter, and presents a strong convexity posteriorly, opposite the upper portion of the third trochanter. The outer trochanter has a flat anterior face, and presents a sharp margin inwards. It is separated from the neck by a deep longitudinal concavity. It is probably much shorter than the head of the femur, about as in Megalosaurus .

	In.
Length of femur restored,	35.5
“ actual,	32.
Transverse extent of condyles,	6.45
Posterior breadth of neck,	6.5
Anterior “ of great trochanter,	3.25
Diameter neck and " “	4.5
“ anterior groove between them (medially),	1.5
Circumference shaft at middle,	11.

This element, compared with that of Megalosaurus , differs in its considerably more slender form, and in its curvature. The femur of the latter genus is very stout, and has a straight axis. The posterioi’ prolongations of the condyles are broken away, but if the external were as small as in Megalosaurus, it was more external, and the popliteal concavity not so abruptly distinguished from the posterior face of the shaft above. This extremity of the bone more nearly resembles that of the Poecilopleurum bucklandii , described and figured by Deslongchamps.

In my original description (Proc. A. N. Sci., 1 86 6) I reversed the position of this bone, I believe incorrectly, which has been observed by Leidy. As it stands broken, the distal extremity is almost identical with that of Hadrosaurus, and the proximal with the trochanter furnishes a very good basis for condyles like those of Megalosaurus ; hence the error.

The relative lengths of the femur and humerus of certain genera of this order may be compared as follows:—

	Humerus.	Femur.	Proportion.
Iguanodon anglicus,	19	33.	.575
Hadrosaurus foulkei,	22.5 in.	41.5	.54.2
Laelaps aquilunguis ,	12 in.	35.5	.33.8
Poecilopleurum bucklandii ,	13	38

Left Tibia.— The tibia is more slender than that belonging to Megalosaurus described by Prof. Owen, and the distal articular surface, instead of being lozenge-shaped, is cuneiform, the inner wide extremity oval rounded. Inner transverse breadth of proximal head one fourth total length. Anterior crest very strong, much incurved, disappearing at between the proximal fifth and fourth of length; internal ridge on proximal half, strong, but not reaching condyles. Posterior condyles separated by a deep notch, inner larger than outer (outer larger, Megalosaurus bucklandii ). Shaft much compressed from before backwards, and distal articulation at right angles to proximal, concave on its interior half. On the exterior face a strong crest extends along the proximal fourth of the length, not reaching the head, which is the point of contact of the slender fibula, and is similar to the same in birds.

	In.
Length of tibia,	30.75
Circumference proximal head,	15.
Anteroposterior diameter do.	7.5
Posterior transverse do. do.	5.5
Transverse length distal condyle,	7.
Longitudinal inner breadth,	2.5
Circumference of shaft at middle,	10.5

These long bones are hollow, with thick walls of dense bone; diameter of medullary cavity at middle of tibia 1.5 inch.

Left Fibula.— Twenty-four inches preserved, proximally concave and dilated; condyle curved, narrow acuminate oval, in profile concave, then rounded descending; length 6 in., median breadth 1.75 in. Just below the condyle on the inside is a deep concavity with abrupt superior and lateral walls. Shaft less flattened below, but slender, reaching a width of 1 1/8 in. The fragment which occupied the most distal position which is preserved, is rather less flattened, but quite convex on the outer face. It is not very unlike in general form the fibula of the ostrich, and like it is continued to the tarsus, closely applied to the tibia. Its proximal half lies on a ridge of the tibia in Laelaps , but when the distal end of the latter expands, the fibula continues directly across the expansion, appressed to the anterior face, in a shallow groove.

I have given the fibula a relation the reverse of that assigned to Hadrosaurus and Iguanodon by Leidy and Owen respectively, that is, I consider their inferior extremity the superior, and vice versa. This relation is coincident with their bird-like affinities, which require a restriction of the fibula distally, not proximally. It also furnishes the requisite extent of articular surface for the condyles of the femur in Laelaps and Hadrosaurus, as well as in Scelidosaurus, according to Owen’s plate. The head of the tibia, alone, is too narrow for the femur in the two genera first mentioned. This structure accords also with Compsognathus , where the fibula is reduced distally.

Tarsus and Metatarsus.— The distal extremity of the tibia is transverse, and much compressed, and does not exhibit any of the usual appearances of an articular surface, neither the reptilian condyle, nor a cotyloid cavity sufficient for an astragalus of the size necessary for an animal of such bulk. A bone, presenting a broad hour glass faced articular surface was discovered with the other remains, and had puzzled the anatomists who had seen it. This piece exhibits along its whole posterior aspect two faces, which form a reentrant angle for a fixed articulation: this is found to have been applied to the extremity of the tibia exactly, and to have been fixed by strong articular ligaments. The medially constricted condyle presenting forwards and a little downwards exhibits an unusual modification of the vertebrate astragalus.

The fibula presents a long and narrow articular surface at the knee, and fitting the tibia by the concavity of its inner face, becomes greatly attenuated at its distal third, where it is, in consequence of an obliquity of its direction applied to the anterior face of the former bone. It may then be supposed to extend to the outer margin of the astragalus, and terminate at the small calcaneum which embraced the outer anterior extremity of the tibia, like an epiphysis. In applying the astragalus, we see that a process projects from its superior margin, which when applied to the face of the tibia occupies with its flat inner face a shallow longitudinal concavity of that bone. This concavity continues across the external expansion of the same, and is continuous with its outer margin in direct line with the position of the fibula. The continually increasing slenderness of the tibia as represented by a large fragment of its distal portion, renders it extremely improbable that it spanned the concave outline of the tibia, to be in contact as in reptiles, with the distal extremity of the tibia, in the usual position of the malleolus, especially as there is no face for contact on the latter. Continued from its point of obvious contact with the external margin of the tibia, it falls nearly into the shallow groove mentioned and into the line of the ascending portion of the astragalus. The latter is broken off at the extremity, but presents a form not very different from the broken slender end ofthe fibula, and is of about the same size.

A reasonable inference is that they were continuous, and I have taken this view. (Proc. Acad., 1866, p. 316.) There is however an objection to this position. One is that the astragalus does not extend across the entire end of the tibia, and presents a smooth surface, perhaps an articular, at its outer extremity. This must have been in contact with a small astragalus or with a malleolar extremity of the fibula. The thin external expansion of the tibia could support but little weight, and as the condyloid convexities of the astragaloid piece are nearly equal, there would seem to be little need of additional condyloid face. Should however the fibula have descended to this point, its course must necessarily have been alongside the ascending process of the astragalus, but not in contact with it. There is no trace of such contact, as the process presents externally an obliquely rounded surface, ending in an angular margin with a posterior flattened face.

Two other examples only of this structure are known in the vertebrata, one of which I find mentioned in Cuvier Ossemens Fossiles, X, p. 204, Tab. 249, fig. 34-5. This author studied the distal extremity of a tibia with applied condyloid astragalus, from Honfleur, which he was not able to assign to any known species or genus, but which he, with usual sagacity, includes in the chapter devoted to Megalosaurus . He however regarded the face of the tibia receiving the condyloid bearing bone, as the inner, instead of the anterior, stating that the tibia is laterally instead of anteroposteriorly compressed, so anomalous is this structure among vertebrates. He regarded the bone as the astragalus, and did not perceive any connection between its anterior ascending apophysis and a fibula, partly because a fibula with distinct distal articulation was received with the same bones.

Gegenbaur’s demonstration of the nature of the ankle joint among birds and reptiles at once makes the nature of the present case clear.*

This tibio-tarsal bone possesses an articular facet on its exterior extremity, probably for conjunction with a calcaneum which supported a small second row tarsal and perhaps rudimental metatarsal and phalange. Its plane is transverse and does not cover the whole extremity, the anterior margin and a knob on the anteroposterior part of the extremity projecting beyond it. Exterior to the middle of the upper margin of this piece and at the internal base of the ascending apophysis, it is perforate, as is the cavity above the condyles of the humerus in the higher apes, and may have received a similar coronoid process of a scaphoides.

As compared with the species examined by Cuvier, this astragalus has a less elevated form; in Cuvier’s specimen the ascending apophysis was flatter, broader, and directed toward the calcaneal facet instead of from it; it lacked the submedian perforation. Its tibial face appears to have been rounded, not angulate. The tibia presented an ascending ridge, to the face of which the ascending apophysis was applied; in the Laelaps aquilunguis there is no ridge, the apophyses reposing in a slight concavity. This apophysis, like the slender portion of the fibula, is composed of dense bone.

Cuvier describes at the same time a bone, of which he says “il ne serait pas impossible que l’os (fig. 39, fut la tete superieur du perone du pied que je viens de decrire.” This piece has a shaft compressed at right angles to the direction of its head, a form so unlike the fibulae of known Dinosauria , including Megalosaurus and Laelaps , as to render such a relation to the before-mentioned tibia, very doubtful. It is probably a metatarsus.

The second example of the clasping astragalus with anteriorly directed condyle is the Poecilopleurum of Deslongchamps. Here the angle between tibia and metatarsus has been even greater than in Laelaps . The ascending anterior ala is broader than in Laelaps , and appears to be complete and not continuous above with the fibula. That it is in contact with the fibula he states thus: “its internal face is applied to the tibia, while its external was without doubt covered in part by the inferior extremity of the fibula.” This, with identity of form between the extremities of the fibula, and of the ascending process of the astragalus, in Laelaps , renders it probable that the relation is similar in the latter. I may add that I suspect that Deslongchamps like others has reversed the relations of the extremities of the fibula. If both the extremities figured by this author belong to it, it is much less attenuated than in Laelaps .

The tibiae figure by Cuvier and Deslongchamps appear to belong to different species. They differ in many respects as figured. The former has a more contracted shaft than the other; its extremity is less oblique; the inferior plate of the astragalus thicker and less produced; the anterior plate in every way smaller. The species should be called Poecilopleurum gallicum . ( Laelaps gallicus m. Pro. Ac. X. Sci., Phil., 1867, 235.)

The direction of the condyle in these genera indicates the articulation of the distal tarsal and metatarsal elements to have been at a considerable angle with the shank of the leg, and that the direction of the whole foot was oblique as in the birds. As the type is in respect to this articulation between that of Iguanodon and that of Compsognathus , we may probably attribute to it a length of metatarsus intermediate between those possessed by these two, a proposition confirmed by the metatarsals of an allied species, L. macropus m, preserved in the Museum of Rutger’s College, New Brunswick, and described by Leidy. These are double the length of the slender phalanges and near one-half that of the tibia, slender and pneumatic.

Among the remaining Dinosauria the two rows of tarsals are distinct and composed of several elements; one of the proximal series articulating with the largely developed fibula as in the Sauria proper. For this I have proposed the name Orthopoda as the tarsal and metatarsal elements do not seem to have been capable of the same degree of flexure on each other as in the Goniopoda and Symphypoda.

Phalanges.— No. 1. An ungual phalange of remarkable size and destructive use. The depth at the proximal articulation is about the same as in Megalosaurus bucklandii (two inches without inferior tuberosity), but the length is considerably greater. Form everywhere compressed, especially at tip; rounded above. Below the articulating surfaces is the point of insertion of a large flexor tendon, a flattened subglobular process, separated by a groove except in front. The groove extends on each side distally on the middle, to the tip. The general form is not unlike that of a rapacious bird, but it is more compressed.

	Inches.
Length on convexity,	9 3/8
Chord from articulatory surface,	6 1/4

Surface slightly striated at the base on one side.

No. 2. Penultimate. Proximally higher than broad, distally broader than high; two elevated articular surfaces proximally, distal condyles separated by a deep groove and much prolonged inferiority; a fossa on each side eccentric to the condyle. Superior outline straight, inferior descending behind.

No. 3. Also penultimate, is flatter and more parallelogrammic in section than the last.

No. 4. Antepenult? more cylindrical, condyles broken.

	Inches.
Length, No. 2,	4.75
Proximal elevation,	1.75
" breadth below,	1.75
Breadth shank below,	1.25
Distal width,	1.25
"" of condyles below,	1.75
No. 3, proximal breadth below,	2.125
Breadth shank below,	1.50
Terminal and inferior breadth distal condyles,	1.875
No. 4, length,	6.

Another phalange of a much larger individual pertaining perhaps to Laelaps , which was accompanied by a platelike bone, is thus described in the Proceedings Academy Natural Sciences, 1866, p. 6:

"Dr. Leidy directed the attention of the members to the specimen of a large phalanx of an extinct reptile, presented this evening by Dr. W. Spillman of Columbus, Miss. It was derived from the cretaceous formation in the vicinity of the latter place, and is remarkably well preserved. It is a first phalanx, and in general form resembles the corresponding phalanges of the Alligator, but is proportionately more robust. The proximal articular surface is moderately concave, somewhat uneven; and in outline is transerve oval with the lower side flat; the distal extremity is provided with a trochlear articular surface and deep pits literally for ligamentous attachment. The animal to which the bone belonged is unknown; it may be conjectured to have appertained to the fore foot of Hadrosaurus. The measurements are as follows:

	In.	Lin.
Length in the axis,	5	8
“ laterally “	6
Transverse diameter of proximal end,	2	11
Vertical " “ “	2	5
Transverse diameter of distal end inferiorly,	2	5 1/2
Vertical diameter at middle of trochlea,	1	6”

The phalanges and tibia figured by Leidy in Cretaceous Reptiles, tab. xvii., 8-11, differ from those from Barnesboro, and, I suspect, belong to another species. Indeed these portions are so uncharacteristic in Reptiles that they cannot be certainly assigned to the genus Laelaps .

Whole Hind Limb.— The femur and tibia together measure 65.50 inches. A method of estimating the length of the metatarsus is by comparison with that of Hylaeosaurus, as described by Prof. Owen. The distal extremity of the inner metatarsus in L. macropus (fig. 13) is much like the same in Hylaeosaurus, while the proximal of the outer is like that of Megalosaurus as figured by Owen, so that I estimate their length together to have been ten inches. The transverse extent of the tibia in the same species is four inches. The latter measurement in L. aquilunquis being seven inches, it gives as the whole length of the metatarsus eighteen inches.

The length of the tarsal region may have been five inches.

The longest digit most probably embraced as in the crocodile, four phalanges. None of the eight phalanges of the genus which have been preserved are of shortened form like the penultimates in the Palapteryx etc., but though from different portions of the toes are all well represented by those of the crocodile. I am disposed therefore to believe that the toes were long, and to attribute to the longest a length of twenty-one inches, measuring the chord of the ungual phalange.

These measurements give for the total length of the extended hind limb, ten inches more than eight feet. This is probably greater in comparison with the total length than in Hadrosaurus, where the elements beyond the tibia are comparatively short. The length of the hind limb in Hadrosaurus foulkii was probably a little over nine feet.

Pubes.— Each pubis has a gentle sigmoid flexure and a subtrigonal section. They are flattened at the inner extremity, and dilated, with a margin at right angles to the shaft; the whole of this extremity is not preserved. It is hollow, while the shaft is dense and heavy. Length 18.5 inches. I am disposed to regard these slender bones as pubes also, because they are homologous with similar bones in Hadrosaurus, whose ischia we are probably in possession of, which are quite different. Moreover the pubes of Hadrosaurus would not support the animal’s weight as ischia, nor would they permit any lateral motion of the caudal column. The tail of Laelaps probably possessed such a motion, and if the ilium be similar to that assigned to Megalosaurus by Huxley, the long pubes if placed in the position of ischia would interfere with such motion.

The elongate ischia of Stenopelix are not dissimilar to those of Laelaps , but in the more nearly allied Compsognathus the pubes are the more elongate.

? Ilium. — Huxley’s statement that the so-called coracoid of Megalosaurus is the ilium, leads us to anticipate a similar form for that of Laelaps . In Megalosaurus it is a semidiscoid plate, the superior margin forming an arc, the inferior furnishing the acetabular and articular surfaces. It has not the elongation of that of the Orthopoda, but is thinner and lighter.

? Sternum.— Very broad, thin, plate like bones have been on three occasions found with Goniopod Dinosauria . One of these was found with the New Jersey, the other with the Mississippi Laelaps . The Mississippi specimen is 13.5 inches long, and presents a thickened margin with convex outline on one side, and thins away to a thin edge at a width of 4 in. 5 lin. One side of this plate is convex, the other concave, and the ossification radiates from the middle of the thickened margin in every direction. There are no traces of contact with diapophyses of a sacrum. The New Jersey specimen, found with the other remains of Laelaps aquilunquis , is merely a piece broken from the thickened margin of a similar, though smaller bone measuring some 4.5 in length and 1.75 in width.

The form of these pieces reminds one of the thin concave anterior expansion of the ilium in gallinaceous and other birds, or if sternal, of the xiphisternal element.

External Form and Posture of Laelaps .— The short fore limbs of this genus suggest at once the habit of using the hind limbs chiefly, yet this disproportion is no sufficient reason therefor, and is seen to exist in the tailless Batrachia, where no such position is assumed. It exists to a less degree among the modern lizards, whose position we well know to be always horizontal.

Laelaps had, however, no doubt an erect position for the following reason: The head and neck of the femur are at right angles to the direction of motion on the condyles, or in the same plane as the transverse direction of the condyles. This indicates that the femur has been flexed, and extended in a plane parallel with that of the vertebral column. The relations of articulation are those of birds and different from those of reptiles, where the directions of the proximal and distal condyles of the femur are oblique to each other, and the proximal, of vertically elongate form, thus allowing the femur to be obliquely directed as regards the axis of the body, so that in a prone position it rested on the ground equally clear of the body and the flexed tibia.

The resemblance of the tibia with its high crest and embracing astragalus, as well as the slender fibula, to those of the birds, confirms this position; so do types of the iliac and sacral structures. The same is suggested by the great bird-like reptile tracks found in many places.

How must a reptilian form with elongate vertebral column and heavy tooth-bearing cranium have stood erect? The elongate form of the femur, as compared with the tibia, is only seen in man, who walks erect; in the birds and kangaroos the femur is very much shorter than the tibia; besides these, no other vertebrates walk on the hind limbs, entirely or in part. The lizards, which are prone, present the long femur exceeding or equalling the tibia.

The bird-like reptile did not, however, exhibit the slight flexure between femur and tibia presented by man. The acetabulum in the known Dinosauria is not or but weakly completed below, or what would be in man anteriorly, indicating that the weight of the body was supported by a femur placed at a strong angle with the longitudinal axis of the ilium; otherwise the head of the femur would be most readily displaced. If, therefore, the ilium were more or less erect, the femur was directed forwards; if horizontal, the femur must have projected downwards. I have shown, however, that the position and therefore the ilium was oblique or erect; therefore the femur was directed very much forwards.*

There are, however, other reasons for believing that the femur was directed forwards, and somewhat upwards from the ilium. One is, that the centre of gravity of an elongate reptilian dorsal and sternal region must have been further forwards than in the shortbodied bird, and therefore the knee must have been further forward, in order to bring the support, i. e., the tibia, etc., beneath it. Another is, that the articulation of the tarsometatarsal bones with the tibia is excessively oblique, requiring that one or both sections of the limb should be very oblique to the vertical line. As the tarso-metatarsal elements support the weight immediately on the ground, and as it is obvious that the leverage moving the great weight of the body on its support must have been the gastrocnemius and soleus muscles extending the tibia on the metatarsal segment as the fixed point; and as there is no indication of correspondingly powerful muscles to flex the metatarsals on the phalanges; it is obvious that the latter has been the more vertical, and the former the more oblique segment. And if the tibial segment has been oblique, for reasons just given, the femur must have been oblique also.*

The length of the femur has had relation to another peculiarity as well, as follows:

In an animal designed to walk erect, it is necessary that the centre of gravity should be transferred as far posteriorly as is consistent with the type. In Laelaps and other Dinosauria we have very elongate pubic and iliac bones, and as I have before described, these appear to have been designed to enclose and support an abdominal mass, in a position beneath the sacrum, and posterior to the position observed in quadrupedal mammals and reptiles. We would thus have a prominent keeled belly between the femora, supported by elongate curved ischia behind, and slender pubes directed downwards in front. In Poecilopleurum the space between the latter and the sternum was occupied by abdominal ribs. The length of femur places the arc through which the knee moves beyond this projection.

The confluence of a greater number of vertebrae to form a sacrum seen in this order and in the birds, would seem to have a direct relation to the support of the above mentioned greater weight by it, than in horizontal vertebrata, where the weight is distributed throughout the length of the vertebral column.

The shifting of the neural arches backwards, seen in the same orders, pointed out by Owen, would have a mechanical relation to the same necessity; i. e., their partial transfer over the intervertebral spaces naturally tending to strengthen the union of the sacral elements.

The foot need not however have been placed precisely beneath the centre of gravity of the body, as the animal was furnished with a tail of greater or less weight. This member bears however little proportion to the great size of those seen in Iguanodon, Hadrosaurus, etc., but exhibits a commencement of the reduction which is so striking among the birds.

The proportions of the metatarsus are only to be ascertained by an examination of those of allied species, as L. macropus and Megalosaurus bucklandii . As all the other bones are more slender than those of the latter, so were no doubt these bones longer in proportion to their breadth. I have estimated it above, as equal to a little over half the tibia.

The digits in the genus Laelaps have not in all probability, been more than three. The less bird-like forms of Hylaeosaurus and Iguanodon, have had according to Owen, but three metatarsals, and it is not according to the rule of successional relation, that there should be any repetition of a reptilian character, in a point of prime importance in measuring the steps of succession between reptiles and birds. Laelaps and probably Megalosaurus , also, had but three digits directed anteriorly, and a fourth rudimental.

It is true that Deslongchamps ascribes five digits to Poecilopleurum after a careful study of abundant material. He was however much more impressed with the crocodilian affinities of that reptile than with any other, and did not recognize the avine in the astragalus. It seems to me quite possible that one of his toes can be dispensed with, for example the second, of which but one phalange is said to remain. If we ascribe the fractured extremity of the bone regarded (Tab. VIII., p. 6,) as the first phalange of the fourth digit, to the metatarsal of the same, the phalange referred to the second may find another place. The fifth digit also rests on the evidence of one phalange only. Though the reasoning of Deslongchamps in referring these pieces is good, it seems to me that renewed study might result in ascribing to his genus, three toes anteriorly and one appendicular, his first.

The predominance of reptilian characters in the Dinosauria as indicated by the structure of the vertebrae, and other points, renders it probable that the vertebral column did not present that remarkable flexure where the cervical and dorsal series are joined, which is seen in the birds, but rather that they were more or less continuous, and formed a continuum from the sacrum to the nape. The cervicals may have been somewhat elongated as in some birds, yet this is not probable in view of the necessary balance to be preserved, which would not admit of much projection of the cranium anteriorly. The cervicals of Hadrosaurus are not so long as in the modern Varani; in Iguanodon they are similar, while their rather oblique articular faces indicate the elevation of that region, and of the position of the cranium. In the case of these animals, there is not the same necessity for a long neck as in the birds, for even in Laelaps and other genera which probably never used the fore limbs in progression, they furnished a support to the body when the head was employed in taking food, etc., in the ground.

The caudal region affects the general proportions of a vertebrated animal materially.

In Laelaps it is shorter than in any known Dinosaur, measuring less than the hind limb by a foot. It was cylindrical, slender towards the tip, and in fact not unlike that of a dog, and probably capable of motion similar to the latter. When the Laelaps stood erect, the tail would trail its extremity on the ground, but could furnish little support.

Comparison with other Dinosauria .— The species with which detailed comparison can be made, are the Poecilopleurum bucklandii Deslongchamps, and Megalosaurus bucklandii Mantell. All three were of nearly similar size. The Poecilopleurum is better known than the Megalosaurus, and furnishes many similar parts. Thus the humeri possess the the same disproportionately small size, the extremity of the tibia is similarly expanded and flattened, and is similarly embraced by the astragalus. There are, however, abundant specific differences in all the bones described by Deslongchamps. In the same manner the Laelaps aquilunguis presents abundant specific difference from the Megalosaurus bucklandii . The slender, curved femur differs from the massive straight one of the latter; the tibia is more slender, and more flattened distally; its extremity is wedge-shaped, not rhombic as in European species. The claws of the Megalosaurus are relatively shorter and less curved.

The generic relations with these two types must be understood. Laelaps is obviously distinct from Paecilopleurum in the structure of its feet. In the former the phalanges are slender, in the latter massive, and mostly broad. The claws are more different; in the former compressed and hooked; as broad as deep in the latter, and but little curved. They are prehensile in the former, in the latter not at all, or adapted only for defense; they present a very small point of insertion, compared with the large knob of the former; they also exhibit a deep groove on the side, which is weak in Laelaps . The difference in this respect is about that between a raptorial and rasorial bird.

As compared with Megalosaurus , Laelaps probably had very short fore limbs. I have pointed out the difference in the femur, which is perhaps no more than specific, though this cannot be positively asserted. The difference in the form of the extremity of the tibia I suspect also to indicate more than specific difference. The bone supposed by Owen (Palaeontographical Society) to be scapula furnishes means of estimating the size of the humerus. The glenoid cavity is some six inches in diameter, indicating a humerus of four times the size of that of Laelaps at least. But this bone is more likely to be an ischium than scapula. The claws also of Megalosaurus are intermediate between those of Laelaps and Poecilopleurum , being less compressed and hooked than in the first.

Size.— In estimating the length of this reptile we have the lengths of the limbs and tail, and proportions of parts of the jaws to rely on. There is some reason to believe that the lengths of the hind leg and the tail were similar. In erect animals, as the Kangaroos and Ostrich, the length of the vertebral column anterior to the sacrum about equals the length of the hind limb. In the present form the limb is increased by the greater length of the femur than in either, but is shorter than that of the bird by the abbreviation of the metatarsals. The proportions would then remain about the same as in the bird were it not that a larger head has evidently been borne upon the cervical vertebrae than in that class, and more as in the Kangaroo. It appears, then, that the increased length of the femur in Laelaps may be added to the proportions of the Kangaroo, thus giving a nearer equality between the lengths of the hind limb and the body and head together. The length would then be eighteen feet, divided as follows:

	Ft.	In.
Tail,	8	6
Body and neck,	6	10
Head,	2
	17 ft.	4 in.

This is probably the size of the Barnesboro individual, which is in all probability young, as the sacral vertebrae are entirely ununited. The phalange from Mississippi, above described, is very much larger than any of the former, and may have belonged to an adult animal. In any case it indicates a gigantic reptile of twenty-three feet or more in length.

The femur of the young individual is as long as that described by Owen (Palaeontographica) as belonging to Megalosaurus. As that genus was probably more bulky anteriorly than Laelaps , its length as compared with the dimensions of the hind limb is greater. If however it approached Laelaps in proportions as is probable, the length of thirty feet assigned to it, appears too great. In fact it can hardly have been larger than the Mississippi, or adult Laelaps aquilunguis .

Thus the original estimate of the lengths of these carnivorous Dinosaurs is still further reduced. Owen accomplished part of this by estimating on the mammalian, and rejecting the reptilian type; the introduction of the avine element places the proportion at about the proper point in respect to the Goniopoda at least.

The elevation of the head of Laelaps would no doubt depend more upon the pleasure of the animal, than in a more quadrupedal form. Nine feet above the ground is a probable estimate for the young one, and twelve for the adult.

Movements.— The mind will picture to itself the actions and habits of such strange monsters as the Dinosauria , and in respect to some of the genera there is considerable basis for speculation.

That monsters walking on two posterior limbs have inhabited the earth has been familiar to all since the publication by Hitchcock and Deane of the histories of the great foot tracks of the Triassic Red Sandstone of the Connecticut Valley. Such tracks have been discovered by John Smock in the same formation in New Jersey, and by Dr. Chas. Hitchcock in Pennsylvania. Prof. Hitchcock ascribed the tracks described by him to birds. Prof. Agassiz* expresses the belief that they were made by vertebrates combining characters of existing classes, perhaps of Reptiles and Mammals, rather than by birds. Now a carnivorous Dinosaur probably allied to Laelaps , as proven by a portion of the jaw with teeth, in the Academy’s Museum, the Bathygnathus borealis of Leidy, has left its remains in the red sandstone of Prince Edward’s Island, of the same age, and we safely conclude that some of the large clawed biped tracks of Hitchcock resemble those of that animal. Dr. Leidy has suspected that this would prove to be the case, as he asks† “was this animal probably not one of the bipeds which made the so-called tracks in the sandstone of the Connecticut Valley?” This inquiry was after an examination of the form of Laelaps , answered in the affirmative. I have ascribed these tracks to Reptiles allied to Laelaps ,‡ and Huxley believes also that they were made by Dinosauria .§

The creatures which strode along the flats of the Triassic estuary have been various in species and genera, as pointed out by Hitchcock. Some were purely biped; some occasionally supported themselves on a pair of reduced fore limbs. There are impressions where these creatures have squatted on their haunches. One can well imagine the singular effect which these huge gregarious reptiles would produce standing motionless, or marching or wading slowly along the water’s edge, ready for a plunge at passing fishes or swimming reptiles. But in the active pursuit of terrestrial prey did such an animal as the Laelaps run like the Ostrich, or leap like the Kangaroo. So far as the triassic tracks go, there is little evidence of leapers, chiefly runners, fell upon an exhausted quarry. Or were they only carrion eaters, tearing and devouring the dead of age and disease? Probably some were such, but the prehensile claws of Laelaps are like instruments for holding living prey.

Laelaps has a long femur; those great leapers the Kangaroos have a short one; the cursorial birds, however, have a similarly short femur, but they do not leap. So this form is not conclusive. The modern Iguanas have a long femur, and they all progress by their simultaneous motion; they only leap; but man with his long femur runs only. The question, then, does not depend on the form of the femur.

I have suggested, on a former occasion, that Laelaps took enormous leaps, and struck its prey with its hind limbs. I say, in describing it, “ the small size of the fore limbs must have rendered them far less efficient as weapons than the hind feet, in an attack on such a creature as Hadrosaurus; hence perhaps the latter were preferred in inflicting fatal wounds. The ornithic type of sacrum elucidated by Prof. Owen, suggests a resemblance in the use of the limb.”

There were but few animals then living which could afford long pursuit on land, so far as known, excepting among the Dinosauria of that day. The Laelaps had to contend with hard-shelled turtles or armored crocodiles, or the swift sea-saurians. These it must capture by sudden movements, as it is not likely that its grasping toes furnished much natatory power.

The lightness and hollowness of the bones of the Laelaps arrest the attention. This is especially true of the long bones of the hind limbs; those of the fore limbs have a less considerable medullary cavity. In this respect they are quite similar to those of Coelosaurus Leidy , of which its describer remarks that “the medullary cavity of the tibia is large, and the walls thin and dense,” “being intermediate in this respect between the characters of the Mammals and Birds.”

The mutual flexure, as well as the lightness and strength of the great femur and tibia are altogether appropriate to great powers of leaping. The feet must have been elongate, whatever the form of the tarsi; the phalanges, or toe bones were slender, nearly as much so relatively as those of an eagle, while the great claws in which they terminated were relatively larger and more compressed than in the birds of prey. There was no provision for the retractibility observed in the great carnivorous mammalia, but the size of the inferior basal tuberosity indicates the insertion of a great tendon of a powerful flexor muscle. The slight grooves at the base, and deeper one on each side of the phalange, indicate the usual horny sheath, which, prolonging the point of the claw, would give it a total length of ten inches.

The tail was moderately long, rounded and strong, and not so much a support as capable of striking a blow and of throwing an enemy within reach of the kick or grab of the terrible hind leg.

The fore limbs must indeed have been of very little use, and it is very difficult to imagine an animal both running and seizing the prey it overtakes, with the hind limb. If it were not a carrion feeder it must 'have leaped. We are informed by Hochstetter* that the Apteryx leaps with the utmost ease over objects two and three feet in height, that is, higher than its head. Huxley suggests that the Compsognathus “ hopped ” along on its hind limbs. The bulk of Laelaps is no objection to its leaping, for the giant extinct kangaroos, Macropus atlas and titan, found in the postpliocene caves of Australia, did not fall far short of these reptiles, in this respect. We may add that Laelaps had smaller allies, as L. macropus one-half, and Coelosaurus antiquus one fourth or fifth the size, whose remains so far as they go indicate an identity of habit. Deslongchamps says of Poecilopleurum bucklandii that it “ could project itself with prodigious force, as a spring which unbends itself; but this could not have been on a solid surface, since the fore limbs are too weak to resist the shock of the fall of such a heavy body.” He supposed it to be marine in its habits, accustomed to battling a stormy sea. However his objection to leaping on land is obviated by our hypothesis of its erect attitude, and its exclusive use of the hinder limbs, the weight always falling on the latter.

The disproportion between the fore and hind limbs of the Iguanodon, together with the compressed form of the tail suggested to Prof. Owen an aquatic habit, a relation of proportions of limbs to habit seen in the tailless Batrachia. The discovery of the massive short-toed foot of the Iguanodon subsequently, has lent little countenance to the supposition of its entire adaptation to aquatic life. Dr. Leidy has regarded the still greater disproportion in the case of the Hadrosaurus as an index of a habit like that of the Kangaroos (Macropus, etc.), and that that moster rested in an oblique position on the hind limbs and tail, and reached upwards with its muzzle and short fore limbs to the foilage on which it fed. He seems also to have regarded it as aquatic as he adds, “on the shores of the ocean in which it lived.” These genera could not have been aquatic in any great degree, as the form of the toes was too stout, and they could have been too little separated to allow of a natatory web.

The bulk of the species, as compared with that of Hadrosaurus, illustrates again the law observed'in the relation between Felis and Bos, and the other raptorial and herbivorous Dinosauria .

In the same chocolate greensand bed the workmen found a femur of Hadrosaurus foulkii, smaller than that described by Dr. Leidy; also portions of Mosasaurus dekayi. Either on the chocolate or in the green stratum above it, remains of Bottosaurus harlani, Hyposaurus rogersi Owen, and Holops gavials of perhaps four species, with Cimoliasaurus magnus Leidy, were found.

The only molluscs which occurred with the remains of Laelaps were Baculites ovatus and Cucullaea vulgaris. Ten feet above is a stratum of Ostrea vesicularis and Terebratula harlani.

Synonymy.— The only doubt as to the proper name of this genus, has arisen with reference to the description of the genus Dinodon by Leidy. I have cleared this matter up in Silliman’s Journal, 1868, p. 415, as follows:

In the Transactions of the American Philosophical Society, xi. p. 143, Dr. Leidy describes a large, carnivorous reptile allied to Megalosaurus, under the name of Dinodon Horridus. He assigns to it, with some expression of doubt, teeth of two distinct forms, viz: some having a lenticular transverse section, with crenation on the two margins in part, and others having a lenticular section truncate to a greater or less degree, in place of one of its angles, and therefore crenate on three edges in part.

If Dr. Leidy had left the matter undecided as to which of these he regarded as the type of the genus Dinodon , the almost universal practice of naturalists would refer the name to that form which should not be first thereafter discovered to be distinct, and named.

I have been of the opinion that the two forms of teeth included by Leidy under the head of Dinodon really belong to distinct animals, and Leidy is also of that opinion. In 1866, in describing the genus Laelaps (Proc. Acad., p. 279), I said, “ The genus Laelaps belongs to the family Dinodontidae which is characterized, * * by its compressed, sabre-shaped teeth. It differs * * from Dinodon in that teeth of the latter have two posterior serrate edges separated by a posterior plane.” This, then, according to the usage of naturalists establishes the name Dinodon for the truncate teeth and Laelaps for the two-edged.

Dr. Leidy however in an essay published in Proc. Academy Nat. Sci., 1868, p. 198, in expressing his belief in the distinctness of the two genera, states that “teeth of like shape” (i. e. like Megalosaurus) referred by me to Dinodon alone belong to this genus, and names the species represented by the truncate teeth, or the true Dinodon horridus , Aublysodon mirandus . He then goes on to say, “Future discovery may prove Laelaps and Dinodon identical,” and on p. 199 * * “An enemy which may perhaps on nearer comparison of corresponding parts prove to be another species of the same genus until now supposed to be different, under the names of Dinodon and Laelaps .” It is thus sufficiently obvious that the proposition is to refer Laelaps a.s a synonyme of Dinodon . It appears to me, on the other hand, that this is contrary to the rules of nomenclature, and the principles which lie at their root, and that the name Aublysodon is a synonyme of Dinodon .

This is however on the supposition that Leidy had left the question open or uncertain, as to which of the two forms of teeth was characteristic of his genus Dinodon . I think however he has not left it undecided, and I am supported in this by the opinion of Von Meyer.

The teeth of Laelaps both from New Jersey and Nebraska do not differ from those of Megalosaurus, while those of Dinodon do. It was not to be supposed that Dinodon was established on teeth of the former character, as the practice of describing species and genera, without a basis of distinctive characters is an unusual and bad one, and ought not to be tolerated in natural science.

In describing Dinodon, Leidy says the Laelaps-like teeth resemble those of Megalosaurus, and in his recent article in the Proc. Academy (p. 198), that they are “identical in character with those of Megalosaurus.”

He moreover specifies that the truncate teeth of Dinodon are really those that characterize it, in the followingwords: “ as the entire dentition of Megalosaurus has not yet been ascertained, it may turn out to be the case that in other parts of the jaws than those known, it possesses teeth like the ones above described as peculiar. Should on future discovery such a condition of things be proved to exist, Dinodon would then cease to be anything more than a second species of Megalosaurus.” The truncate teeth are then the “peculiar” feature of Dinodon , and all that prevents the species from being referred to Megalosaurus.

Von Meyer has understood this language as I have, and has believed that the teeth now ascribed by Leidy to Aublysodon are really characteristic of Dinodon . He says (Palseontograpliica, vii, p. 267) that some of the teeth “ indicate such peculiarity, that Leidy, who has made the investigation, thought it necessary to characterize the animal as distinct from Megalosaurus, under the name of Dinodon horridus.

It is therefore evident that the Laelaps-like teeth described under Dinodon , are really those that require a new name, if any. I will not give them a name however, since there is no evidence that they differ from either Megalosaurus or Laelaps , though of course the probability is, that they belong to a species of the latter genus.

Although Aublysodon would thus be a synonyme of Dinodon , it is not an altogether useless name, since the latter was given years ago to a genus of serpents by Dumeril and Bibron, and may therefore be suppressed.

The classification and characters here employed in treating of the Dinosauria , were embraced in the original essay included in the present one, which was read, and the contents communicated verbally, before the Academy of Natural Sciences in the spring of 1867.

This point is alluded to partly because the portion of the original essay on the Dinosauria has been in part anticipated by the publication of a lecture by Prof. T. H. Huxley before the Royal Society of Great Britain, bearing date February 7, 1868. The tenor and result of the studies of Prof. Huxley were the same that followed my own, and the details of his reasoning are thus published prior to mine. The position of the ischia and pubes in the Dinosauria ,

I had already believed to be as herein explained, and as stated by Prof. Huxley, though I had not been able, as he has, to place the elements called by Owen clavicles in the position of iscliia, but rather of pubes. Prof. Huxley’s determination of the ilium of Megalosaurus, a point of the greatest importance, was new to me, and I have added this and other allusions to his address. Other than these I have added nothing to the history ot Laelaps since its original preparation beyond a few points in the restoration which grew only out of my original observations.*

It is not however a matter of surprise, that with the increased number of students at the present time, the same subject should be under cotemporary investigation, and the same results be brought out at the same time.