Discoscaphites Meek, 1870

LANDMAN, NEIL H., JOHNSON, RALPH O. & EDWARDS, LUCY E., 2004, Cephalopods from the Cretaceous / Tertiary Boundary Interval on the Atlantic Coastal Plain, with a Description of the Highest Ammonite Zones in North America. Part 1. Maryland and North Carolina, American Museum Novitates 3454 (1), pp. 1-64 : 37-56

Genus Discoscaphites Meek, 1870

TYPE SPECIES: Ammonites conradi Morton, 1834: 39 , pl. 16, fig. 3, by original designation.

Discoscaphites gulosus ( Morton, 1834)

Figures 12C–J, 16

Ammonites conradi var. petechialis Morton, 1834: 39–40 , pl. 16, fig. 1.

Ammonites conradi var. gulosus Morton, 1834: 39 , pl. 16, fig. 2.

Ammonites conradi var. navicularis Morton, 1834: 40 , pl. 19, fig. 4.

Discoscaphites gulosus ( Morton, 1834) . Landman minardi , n.sp., USNM 525324. E, Ventral; F, left lateral. P, Q. Eubaculites carinatus ( Morton, 1834) , USNM 525332. P, Ventral; Q, left lateral. R. Eubaculites cf. E. carinatus ( Morton, 1834) , USNM 525333, right lateral. All figures ×1.

and Waage, 1993: 212, figs. 156, 157, 159, 160, 167–180 (with full synonymy).

Discoscaphites gulosus ( Morton, 1834) . Cobban and Kennedy, 1995: 29, figs. 10.4, 10.5, 19.20– 19.24, 20.8–20.10, 20.14–20.17, 21.18–21.21.

Discoscaphites gulosus ( Morton, 1834) . Kennedy et al., 1997: 21, figs. 20K–O, 21D, E.

Discoscaphites gulosus ( Morton, 1834) . Kennedy et al., 2000: 26, fig. 9G–I.

TYPE: The holotype is ANSP 51552 from the Prairie Bluff Chalk at Prairie Bluff , Alabama .

MATERIAL: There are five specimens from the Peedee Formation, Brunswick County, North Carolina. Four of them ( AMNH 48551 , 48553 , 48557 , and 50328) were collected from the Todd Marl Pit, approximately 2 km west of the Shallotte River , and one of them ( AMNH 50365 ) was collected from John D. Long County Park, Rt 33, 1.8 km south of Rt 17, near Wilmington .

MACROCONCH DESCRIPTION: AMNH 48551 is an internal mold of a macroconch 55.6 mm in diameter, missing part of the hook (fig. 12H–J). The umbilical seam of the body chamber is straight in side view. The whorl section at the base of the body chamber is compressed subquadrate with a ratio of whorl width to height of 0.58. The flanks are subparallel and broadly rounded. The ventrolateral shoulder is abruptly rounded, and the venter is narrow and well rounded. The whorl section becomes more robust in passing into the body chamber; the ratio of whorl width to height at midshaft is 0.67. The inner flanks are broadly rounded and divergent and the outer flanks are nearly flat and convergent. The ventrolateral shoulder is abruptly rounded and the venter is nearly flat.

The phragmocone bears ribs and tubercles, although the tubercles on the flanks are poorly preserved. The ventrolateral tubercles become more widely spaced toward the base of the body chamber; the distance between the two most adoral tubercles is 5.5 mm. The ornament on the body chamber is slightly better preserved on the left side and consists entirely of tubercles. There is an umbilicolateral row, three flank rows, and a ventrolateral row. All of the tubercles are fairly strong, although eroded, and widely spaced. The tubercles on the outermost flanks are slightly more prominent than those on the ventrolateral margin.

AMNH 48557 is a fragment of the right side of the adoral part of the shaft of a body chamber, probably a macroconch (fig. 12C, D). Ribs swing forward crossing the venter with a weak adoral projection; there are 9 ribs/cm on the venter. Five rows of tubercles are present, including an umbilicolateral row, three flank rows, and a ventrolateral row. The umbilicolateral and outermost flank rows are the most prominent. The distance between consecutive tubercles in the outermost flank row is 9.2 mm. The tubercles in the ventrolateral row are slightly more closely spaced with a distance between consecutive tubercles of approximately 7 mm.

AMNH 50365 is a piece of a mature phragmocone and adapical part of a body chamber, probably of a macroconch, half of which is still stuck in the matrix (fig. 16). The umbilicus is exposed on the left side and is 4.0 mm in diameter. Part of the umbilical seam of the body chamber is preserved and is straight in side view. The whorl width and height near the adoral end of the phragmocone are 18.2 and 21.6 mm, respectively; the ratio of whorl width to height is 0.84. The flanks are broadly rounded, the ventrolateral shoulder is abruptly rounded, and the venter is nearly flat with a low ‘‘keel’’ in the middle. Ribs are strong, broad, and rectiradiate or prorsiradiate on the inner half of the flanks, with branching and intercalation at approximately midwhorl height. Ribs bear six rows of tubercles including the ventrolateral row. Tubercles in the outermost flank and ventrolateral rows are nearly equal in size; the distance between consecutive tubercles in each row is approximately 3 mm. Outer ventrolateral tubercles are paired on either side of the venter with each pair connected by a low, broad rib.

MICROCONCH DESCRIPTION: AMNH 48553 is an internal mold of a body chamber 54.4 mm long slightly crushed in on the adapical end (fig. 12E–G). The aperture is well preserved and shows a deep constriction and a moderately strong adoral projection of the venter. The whorl section is subquadrate at midshaft with an intercostal ratio of whorl width to height of 0.66. The inner flanks are slightly concave and divergent and the outer flanks are broadly convex and convergent. The ventrolateral shoulder is fairly abruptly rounded and the venter is narrow and broadly rounded. The whorl section becomes more quadrate toward the aperture with an intercostal ratio of whorl width to height of 0.76. The flanks are nearly flat and subparallel and the venter is broad and nearly flat.

The ornament is better preserved on the right side. A few ribs are present on the adapical end of the specimen. They appear at the umbilical shoulder and swing forward on the inner flanks, backward on the outer flanks, and then forward again on the ventrolateral shoulder. The umbilical shoulder bears three elongate bullae, the middle one of which is the most prominent. There are two rows of weak, irregularly spaced tubercles on the inner flanks, a row of stronger tubercles on the outer flanks, and a slightly weaker row of tubercles on the ventrolateral margin. The outer flank row consists of six more­or­less evenly spaced tubercles; the distance between consecutive tubercles at midshaft is 7 mm. The ventrolateral row consists of eight tubercles, which are not as regularly spaced as those of the outer flank row; the distance between consecutive tubercles at midshaft is 5 mm. Except for the adapical end of the specimen, the outer flank tubercles are stronger than the ventrolateral tubercles, but this may be an artifact of preservation. The outer flank tubercles extend slightly adoral of the ventrolateral tubercles and both rows disappear on the hook. The flanks of the hook are covered with dense ribs that swing slightly backward at the ventrolateral shoulder and then forward, crossing the venter with a moderately strong adoral projection. There are 10 or 11 ribs/cm on the venter.

DISCUSSION: Of these specimens, only AMNH 50365 (fig. 16) is as highly ornamented as samples of this species from the Severn Formation (e.g., Kennedy et al., 1997: figs. 20K–O, 21D, E). AMNH 48553 (fig. 12E–G) displays an interesting combination of characters. The presence of multiple rows of tubercles plus closely spaced ribbing on the hook with a relatively strong adoral projection on the venter suggest kinship with Jeletzkytes (see, e.g., Kennedy et al. [1997: figs. 22A–C, 23D, E] for illustrations of Jeletzkytes nebrascensis from the Severn Formation). However, an important feature of this specimen is that the outer flank tubercles are stronger than the ventrolateral tubercles on most of the body chamber, which is more characteristic of Discoscaphites and Trachyscaphites than Jeletzkytes . We therefore treat this specimen as a microconch of D. gulosus , closely similar in morphology to the co­occurring macroconchs.

OCCURRENCE: Peedee Formation, Brunswick County, North Carolina; top of the New Egypt Formation and as reworked material at the base of the Hornerstown Formation, Monmouth County, New Jersey (Landman et al., in prep. a); New Egypt Formation, Gloucester County, New Jersey (Kennedy et al., 2000); Severn Formation, Prince Georges County, Maryland ( Kennedy et al., 1997); and Prairie Bluff Chalk, Alabama and Mississippi ( Cobban and Kennedy, 1995). In the Western Interior, Discoscaphites gulosus occurs in both the Hoploscaphites nicolletii and Jeletzkytes nebrascensis zones in the Fox Hills Formation, South Dakota ( Landman and Waage, 1993).

Discoscaphites iris ( Conrad, 1858)

Figures 15A, B, G–O , 17A–G, 18R

Scaphites iris Conrad, 1858: 335 : pl. 35, fig. 23.

Scaphites iris Conrad. Whitfield, 1892: 265 , pl. 44, figs. 4–7.

Discoscaphites iris (Conrad) . Stephenson, 1955: 134, pl. 23, figs. 23–30.

Discoscaphites iris ( Conrad, 1858) . Kennedy and Cobban, 2000: 183, pl. 3, figs. 3–35, text­fig. 5.

TYPE: The holotype , ANSP 50589 , is the original illustrated in Conrad (1858: 335, pl. 35, fig. 23). It is from the bluffs of Owl Creek , Tippah County, Mississippi .

MATERIAL: There is one specimen ( MAPS A2060 c1) from the Severn Formation, AMNH loc. 3252, Kent County, and six specimens ( USNM 525325–525330 ) from the Severn Formation, Round Bay , Anne Arundel County , Maryland. Three of the specimens from Round Bay ( USNM 525326–525328 ) are pinkish­buff in color, suggesting that they are weathered. It is possible that they are from a different horizon than the other specimens from Round Bay , but there is only one label for the entire lot .

MACROCONCH DESCRIPTION: USNM 525325 is a fairly complete, although badly worn and slightly crushed, robust specimen 43.7 mm in diameter (fig. 15A, B). The right side of the phragmocone is still attached to the matrix. The phragmocone is ornamented with fairly coarse, flexuous ribs that bear four rows of tubercles of which the umbilicolateral and inner and outer ventrolateral tubercles are the most conspicuous. The distance between out­ er ventrolateral tubercles on the adapical end of the specimen is 2 mm. The hook of the body chamber is eroded but the shaft preserves umbilicolateral, midflank, and inner ventrolateral tubercles, of which the umbilicolateral and midflank tubercles are the most prominent. The outer ventrolateral tubercles are worn away.

USNM 525328 is a crushed fragment of a body chamber, possibly of a macroconch, with what appear to be four rows of large, eroded tubercles (fig. 15I).

MAPS A2060c1 is a fragment of the midshaft of a large, slightly inflated body chamber with all of the right side missing (fig. 18R). There is a row of umbilicolateral bullae and three rows of tubercles although almost all of the outer ventrolateral tubercles are worn away. Four prorsiradiate umbilicolateral bullae are spaced at approximately equal distances of 4–4.5 mm. Two relatively prominent midflank tubercles occur on the adapical portion of the specimen followed adorally by three much weaker, radial swellings spaced at distances of approximately 4 mm. Five inner ventrolateral tubercles are preserved on the specimen and are evenly spaced at distances of 4.5–5.5 mm. At midshaft, the distance between the umbilicolateral bullae and the midflank tubercles (6 mm) is equal to that between the midflank tubercles and the inner ventrolateral tubercles, which is greater than that between the inner and outer ventrolateral tubercles (5 mm).

MICROCONCH DESCRIPTION: USNM 525326 is a worn, slightly distorted adoral piece of a body chamber 33.6 mm long (fig. 15N, O). The ornament is better preserved on the right side. There are four rows of tubercles that occur on coarse, poorly defined ribs that become more closely spaced toward the aperture. Only two umbilicolateral tubercles are preserved. Of the other rows, the inner ventrolateral tubercles are the largest.

USNM 525329 is part of the adoral half of a body chamber with the left side still embedded in the matrix (fig. 15G, H). The umbilical seam is curved in side view and matches the curve of the venter, indicating it is a microconch. The umbilical wall is flat and gently inclined outward and the umbilical shoulder is abruptly rounded. The inner and middle flanks are nearly flat and slightly convergent and the outer flanks between the inner and outer ventrolateral tubercles are broadly rounded and more steeply convergent. The ventrolateral shoulder is fairly abruptly rounded and the venter is broadly rounded.

Four rows of tubercles are present. The umbilicolateral row is perched on the umbilical shoulder and consists of three tubercles, the middle one of which is the most prominent one on the specimen. There are four midflank, four inner ventrolateral, and five outer ventrolateral tubercles preserved. The outer ventrolateral tubercles are slightly more subdued than the inner ones. The distance between consecutive tubercles in each row is 5–5.5 mm. The distance between tubercle rows on the middle of the specimen starting with the umbilicolateral tubercles is 5.5, 4.5, and 4 mm. The distance between outer ventrolateral tubercles on either side of the venter is 4 mm.

DISCUSSION: Although fragmentary, all these specimens conform to the description of Discoscaphites iris , notably in having four fairly prominent rows of tubercles. They are indistinguishable from specimens of this species from the Owl Creek Formation, Mississippi (fig. 17A–G).

OCCURRENCE: Upper part of the Severn Formation, Kent and Anne Arundel Counties, Maryland. This species occurs in New Jersey in the top of the New Egypt Formation and as reworked material at the base of the Hornerstown Formation, near Eatontown, northeastern Monmouth County (Landman et al., in prep. a); in the top of the New Egypt Formation in the Crosswicks Creek Basin, southwestern Monmouth County (Landman et al., in prep. c); and in the top of the Tinton Formation and as reworked material at the base of the Hornerstown Formation near Freehold, central Monmouth County (Landman et al., in prep. b). It occurs on the Gulf Coastal Plain in the upper part of the Owl Creek Formation and as reworked material at the base of the Clayton Formation in Mississippi, Tennessee, and Missouri ( Stephenson, 1955; Sohl, 1960, 1964; Kennedy and Cobban, 2000). This species denotes the D. iris Zone on the Gulf and Atlantic Coastal Plain, which represents the upper part of the upper Maastrichtian, corresponding to the upper part of calcareous nannofossil Subzone CC26b.

Discoscaphites cf. D. iris ( Conrad, 1858)

Figure 15C, D

Compare:

Scaphites iris Conrad, 1858: 335 , pl. 35, fig. 23.

Discoscaphites iris ( Conrad, 1858) . Kennedy and Cobban, 2000: 183, pl. 3, figs. 3–35, text­fig. 5.

MATERIAL: There is a single specimen ( USNM 525323) from the Severn Formation, Round Bay, Anne Arundel County, Maryland.

DESCRIPTION: USNM 525323 is the adoral half of a robust body chamber with the dorsum still attached to the matrix (fig. 15C, D). Part of the aperture appears to be preserved on the right side. There is an umbilical bulge on the middle of the specimen on the left side indicating it is a macroconch. The inner and midflanks are well rounded with a swelling on the midflanks on the left side; the outer flanks between the inner and outer ventrolateral tubercles are broadly rounded to nearly flat. The ventrolateral shoulder is fairly abruptly rounded and the venter is nearly flat.

The preserved ornament consists of fine ribs, umbilical bullae, midflank bullae, and inner and outer ventrolateral tubercles. One prominent umbilical crescentic bulla appears near the dorsal margin on the middle of the specimen. Ribs are indistinct on the adapical half of the specimen, but are conspicuous on the hook. Ribs are sharp and thin and bear radial bullae on the midfanks. Ribs swing gently forward just dorsal of the row of inner ventrolateral tubercles, crossing the venter with a slight adoral projection; there are 12 ribs/cm on the venter. Seven inner ventrolateral tubercles are preserved on the left side spaced at distances of 4.5 mm on the adapical end of the specimen and 3 mm on the adoral end. They become smaller and slightly more bullate toward the aperture. There are nine outer ventrolateral tubercles preserved on the left side; they show the same spacing as the inner ventrolateral tubercles and become smaller and more closely spaced toward the aperture. On the adoral third of the body chamber coincident with the appearance of conspicuous ribbing, the rows of inner and outer ventrolateral tubercles, especially on the right side, are both shifted toward the venter, possibly due to a pathology.

DISCUSSION: This specimen resembles Discoscaphites iris in its robust whorl section and well­developed rows of inner and outer ventrolateral tubercles. However, it differs in that the midflank tubercles are only represented by small bullae and that very fine ribs cover the adoral third of the specimen.

OCCURRENCE: Severn Formation, Round Bay , Anne Arundel County, Maryland .

Discoscaphites minardi , new species

Figures 17H–M, 18A–Q , S­Y, 19–22

TYPES: The holotype is AMNH 47288 , a macroconch, and the paratypes are AMNH 47293 and 50542, both macroconchs, and AMNH 47289 , 47292 , and 47297, all microconchs, from AMNH loc. 3252, the Severn Formation, Kent County, Maryland .

ETYMOLOGY: After James P. Minard, a geologist at the U.S. Geological Survey, who worked on the stratigraphy of the Atlantic Coastal Plain and discovered the locality where this species occurs.

MATERIAL: There are 32 specimens: 10 macroconchs ( AMNH 47281 , 47283 , 47288 , 47290 , 47293 , 47295 , 47299 , 49406 , 50542 , and MAPS A2059 a 1 ); 6 microconchs ( AMNH 47286 , 47289 , 47292 , 47294 , 47297 , and 49426); and 16 specimens too fragmentary to determine the dimorph ( AMNH 47280 , 47282 , 47285 , 47287 , 47296 , 47298 , 47479 , 49407 , 49414 , 49422– 25 , 50536 , and 50537, and USNM 522938 ), from AMNH loc. 3252, the upper part of the Severn Formation , Kent County, Maryland .

DIAGNOSIS: Relatively small, dimorphic species; flanks of body chamber are flat and subparallel to slightly convergent; ornament on body chamber consists of weak, slightly swollen prorsiradiate ribs bearing concave umbilicolateral bullae, very weak, radial midflank swellings, if any at all, and an approximately equal number of inner and outer ventrolateral tubercles; inner ventrolateral tubercles are as strong as or slightly stronger than the outer ventrolateral tubercles.

DESCRIPTION: This species is relatively small with the macroconch approximately 40 mm in maximum diameter and the microconch approximately two­thirds as large. The hook is only slightly reflected with an apertural angle in macroconchs of 40–50°. The shell is compressed with relatively flat flanks; the ratio of whorl width to height at midshaft averages approximately 0.70. There are four rows of tubercles on indistinct prorsiradiate ribs, which are more closely spaced near the aperture. The umbilicolateral bullae are crescentic and become progressively more prorsiradiate adorally. The midflank swellings are weak and elongated radially, although occasionally they are round. In a few instances, they do not exist at all, which may be due to poor preservation. The inner ventrolateral tubercles are usually pointed but sometimes are elongated radially. There are an equal number of outer ventrolateral tubercles, which are as strong as or slightly weaker than the inner ventrolateral tubercles. The tubercles in both rows are evenly spaced at distances of 4–5 mm. The smallest distance between tubercle rows is between the rows of inner and outer ventrolateral tubercles (fig. 22). This distance is as little as half the distance between other, adjacent rows of tubercles. The position of the midflank swellings is approximately midway between the umbilicolateral bullae and the inner ventrolateral tubercles. However, there is some variation depending on the dimorph. In macroconchs, the midflank swellings are slightly closer to the inner ventrolateral tubercles, whereas in microconchs, they are midway between or closer to the umbilicolateral bullae. This difference is probably related to the difference in whorl height between dimorphs.

Because much of the fossil material is poorly preserved and fragmentary, we describe several specimens to document the morphology of this species as fully as possible. Even so, there is no complete adult and only one specimen ( AMNH 47289 ) preserves any details of the hook .

MACROCONCH DESCRIPTION: The holotype AMNH 47288 is an adult specimen 40.9 mm in maximum diameter with the adoral half of the phragmocone and most of the body chamber preserved except for part of the adapical quarter of the shaft and the venter of the hook (figs. 17H, I, 18A–D). The umbilical shoulder of the shaft is straight in side view. The whorl section at midshaft is relatively compressed with a slightly swollen outline. The whorl width and height at midshaft are 13.6 and 20.1 mm, respectively; the ratio of whorl width to height is 0.68. The umbilical wall is steep and sharply convex and the umbilical shoulder is abruptly round­ ed. The inner flanks are broadly rounded and gently divergent, the midflanks are nearly flat and gently convergent, and the outer flanks are broadly rounded and more steeply convergent. The ventrolateral shoulder is fairly abruptly rounded and the venter is very broadly rounded.

Part of the ornament is visible on the outer flanks and venter on the adapical portion of the preserved phragmocone. Ribs are prorsiradiate on the outermost flanks and link to small ventrolateral tubercles that are evenly spaced at distances of approximately 2.5 mm. It is possible that there is a row of inner ventrolateral tubercles but they are difficult to detect because of poor preservation. Ribs are present on the venter of the most adapical part of the preserved phragmocone. They are evenly spaced at distances of 0.75 mm (= 14 ribs/cm) and show a slight adoral projection.

The ornament on the body chamber is weak; the most obvious features are the umbilicolateral bullae and inner and outer ventrolateral tubercles. There are four umbilicolateral bullae on the right side that extend to the aperture. They are strong and arcuate at midshaft where they are evenly spaced at distances of approximately 4.5 mm. They give rise to weak, straight prorsiradiate ribs. Faint radial swellings occur at midflank and are most noticeable on the adoral half of the shaft where they are spaced at distances of approximately 2.5 mm. They may extend onto the hook but this is impossible to confirm because of poor preservation. There is a row of relatively prominent inner ventrolateral tubercles that are spaced at distances of approximately 4–5 mm at midshaft, becoming more closely spaced adorally. A row of slightly less prominent but equally spaced outer ventrolateral tubercles is also present. At midshaft, the distance between the umbilicolateral bullae and the midflank swellings (6 mm) is slightly greater than that between the midflank swellings and the inner ventrolateral tubercles (5.5 mm), which is, in turn, slightly greater than that between the inner and outer ventrolateral tubercles (4 mm) (fig. 22). The venter is worn and does not preserve any ribbing.

Paratype AMNH 47293 is most of an adult 42.0 mm in maximum diameter (figs. 17J, K, 18H–K). It is missing most of the phragmocone, except for the adoral half, and most of the aperture, and it is badly worn on the left side. The body chamber occupies approximately one­half whorl; the apertural angle is 46°. The umbilical shoulder is straight in side view with a very slight bulge. The specimen is somewhat distorted but originally was very compressed. The whorl width and height at the base of the body chamber are 10.9 and 17.3 mm, respectively; the ratio of whorl width to height is 0.63. The whorl section is equally compressed at midshaft; the whorl width and height are 11.9 and 19.7 mm, respectively; the ratio of whorl width to height is 0.60. The umbilical wall is vertical and steeply convex and the umbilical shoul­ der is abruptly rounded. The inner flanks are broadly rounded, the midflanks are flat to slightly concave and gently convergent, and the outermost flanks between the inner and outer ventrolateral tubercles are broadly rounded and more steeply convergent.

The ornament is only preserved on the right side of the body chamber. Tubercles and bullae occur on weak, prorsiradiate ribs. There are four concave umbilicolateral bullae, the most adoral of which is the smallest and occurs at the apertural margin. They are evenly spaced at distances of 3.5–4 mm on the shaft and are linked by weak, straight prorsiradiate ribs to very weak, radial midflank swellings, of which five are visible spaced at distances of approximately 3 mm at midshaft. Due to poor preservation, it is difficult to determine if these midflank swellings extend onto the hook. Ribs are stronger and more closely spaced toward the aperture. There is a row of 13 inner ventrolateral tubercles (allowing for one lost due to preservation) that extend to the aperture (although the apertural lip is missing). These tubercles are evenly spaced on the shaft at distances of approximately 5 mm but become more closely spaced toward the aperture. A row of equally strong outer ventrolateral tubercles is also present but is worn away on most of the shell. On the adapical third of the body chamber where these tubercles are preserved, they are equal in number and spacing to the inner ventrolateral tubercles. At midshaft, the distance between the umbilicolateral bullae and the midflank swellings (6 mm) is slightly greater than that between the midflank swellings and the inner ventrolateral tubercles (5.5 mm), which, in turn, is much greater than that between the inner and outer ventrolateral tubercles (3 mm) (fig. 22). No ribs are present on the venter, although most of the venter is worn away.

Paratype AMNH 50542 is a crushed piece of the adoral part of an adult phragmocone and adapical part of the body chamber (figs. 17L, M, 18S–U). It was probably originally compressed. The phragmocone bears straight rectiradiate ribs that bifurcate on the outermost flanks. On the adapical part of the preserved phragmocone, only the outer ventrolateral tubercles are visible; they become slightly more widely spaced adorally so that the distance between the two most adoral tubercles on the phragmocone is 4 mm. A row of inner ventrolateral tubercles appears at the adoral end of the phragmocone. The distance between inner ventrolateral tubercles at the base of the body chamber is 5 mm.

The ornament on the body chamber consists of fairly strong, arcuate, umbilicolateral bullae, very faint swellings at approximately two­thirds whorl height, and fairly strong inner and outer ventrolateral tubercles. The umbilicolateral bullae are spaced at distances of 5.5–7.5 mm at midshaft. The midflank swellings, of which there are three, are more pronounced on the left side. The swellings are round and faint and are spaced at distances of 3.25–4 mm. The inner row of ventrolateral tubercles is slightly more prominent than the outer row. At midshaft, the inner ventrolateral tubercles are spaced at distances of 5 mm and the outer ventrolateral tubercles at distances of 6 mm. The two rows are very close to each other so that in a few instances, tubercles from adjacent rows share a common base. On the adapical part of the body chamber on the left side where the tubercles in both rows can be counted, there are five tubercles in each row. At midshaft, the distance between the umbilicolateral bullae and the midflank swellings (7 mm) is much greater than that between the midflank swellings and the inner ventrolateral tubercles (5 mm), which is equal to that between the inner and outer ventrolateral tubercles (fig. 22). There is a single errant tubercle between the two ventrolateral rows on the right side, although it may be laterally displaced due to crushing. No ribs are preserved on the venter.

The rest of the macroconchs in the collection are fragmentary. We describe five of them to further document the morphology of the species. AMNH 47281 is a fragment of a compressed body chamber missing part of the adapical end and hook (fig. 18E–G). The umbilical wall is straight in side view. The whorl section at midshaft is compressed ovoid; the whorl width and height are 12.8 and 19.2 mm, respectively; the ratio of whorl width to height is 0.67. The umbilical wall is steep and sharply convex and the umbilical shoulder is abruptly rounded. The inner flanks are broadly rounded and gently divergent, the midflanks are flat and gently convergent, and the outermost flanks are very broadly rounded and more steeply conver­

47286. R, Ventral; S, left lateral. T–W. AMNH 47297. T, Right lateral; U, apertural; V, ventral; W, left lateral. X–Z, a. AMNH 49426. X, Right lateral; Y, apertural; Z, ventral; a, left lateral. b–e. AMNH 47292. b, Right lateral; c, apertural; d, ventral; e, left lateral. f, g. AMNH 47287. f, Ventral; g, left lateral. All figures ×1.

gent. The ventrolateral shoulder is fairly abruptly rounded and the venter is nearly flat.

The ornament on the body chamber is better preserved on the right side and consists of umbilicolateral bullae, very faint midflank swellings, inner and outer ventrolateral tubercles, and convex prorsiradiate ribs on the adoral half of the shaft. Three umbilicolateral bullae are present and are evenly spaced at distances of approximately 5 mm. The midflank swellings are weak, radial, and occur on prorsiradiate ribs. Two swellings are visible spaced 5 mm apart. They are linked by ribs to the inner ventrolateral tubercles. Both rows of ventrolateral tubercles are well developed with the inner row being slightly stronger than the outer row. The distance between tubercles within each row is 4.5–5.5 mm with maximum spacing at midshaft. The numbers of inner and outer ventrolateral tubercles on the fragment are almost the same (8 inner, 9 outer ventrolateral tubercles). At midshaft, the distance between the umbilicolateral bullae and midflank swellings (8.5 mm) is much greater than that between the midflank swellings and the inner ventrolateral tubercles (5 mm), which, in turn, is slightly greater than that between the inner and outer ventrolateral tubercles (4 mm) (fig. 22). The distance between outer ventrolateral tubercles on either side of the venter is 5 mm.

AMNH 47283 is most of the shaft of a body chamber missing the venter and outer flanks on the adoral end (fig. 18V–Y). The whorl section at the base of the body chamber is compressed ovoid; the whorl width and height are 9.1 and 13.9 mm, respectively; the ratio of whorl width to height is 0.65. The whorl section is slightly more depressed at midshaft; the whorl width and height are 11.4 and 16.1 mm, respectively; the ratio of whorl width to height is 0.71. The umbilical wall is steep and sharply convex and the umbilical shoulder is abruptly rounded. The inner flanks are broadly rounded and slightly divergent, the midflanks are nearly flat and slightly convergent, and the outermost flanks are broadly rounded and more steeply convergent. The ventrolateral shoulder is fairly abruptly rounded and the venter is broadly rounded to flat.

The body chamber is ornamented with umbilicolateral bullae, faint midflank swellings, and inner and outer ventrolateral tubercles. The ornament is slightly better preserved on the left side. There is a straight prorsiradiate rib connecting an umbilicolateral bulla and a midflank swelling just adoral of midshaft. The umbilicolateral bullae originate on the umbilical shoulder and become progressively more prorsiradiate adorally. The distance between umbilicolateral bullae at midshaft is 5 mm. There are three weak, elongate swellings on the midflank starting just adoral of midshaft; they are spaced at equal distances of 2.5–3 mm. The inner ventrolateral tubercles are much stronger than the midflank swellings. There are eight inner ventrolateral tubercles preserved on the body chamber fragment; they are spaced at equal distances of 4.5 mm. The outer ventrolateral tubercles are slightly more subdued and are approximately evenly spaced at distances of 4.5–5.5 mm. At midshaft, the distance between the umbilicolateral bullae and midflank tubercles (5.5 mm) is slightly greater than that between the midflank swellings and the inner ventrolateral tubercles (5.0 mm), which, in turn, is much greater than that between the inner and outer ventrolateral tubercles (3.5 mm) (fig. 22). Although the venter is smooth, it is raised into undulations connecting outer ventrolateral tubercles on either side of the venter on the adapical part of the specimen.

AMNH 49406 consists of the adoral part of the phragmocone and adapical part of the body chamber (fig. 19A–C). The right side is better preserved. The whorl section is compressed ovoid at midshaft. The umbilical wall is steep and convex and the umbilical shoulder is sharply rounded. The inner flanks are broadly rounded and divergent, the midflanks are flat to concave and convergent, and the outer flanks are broadly rounded and more steeply convergent. The ventrolateral shoulder is fairly abruptly rounded and the venter is flat.

The flanks of the phragmocone are covered with slightly swollen straight ribs. There are three crescentic umbilicolateral bullae on the body chamber that become progressively more prorsiradiate adorally. The bullae occur on widely spaced, straight to slightly sinuous, prorsiradiate ribs that link to inner ventrolateral tubercles. The two most adoral ribs bear feeble midflank swellings. The ribs weaken and the flanks become smoother in the region between the midflank swellings and the inner ventrolateral tubercles. The inner ventrolateral tubercles are radially elongated and first appear on the adapical part of the body chamber. They become progressively more widely spaced adorally; the distance between tubercles at midshaft is 4.5 mm. The inner and outer ventrolateral tubercles are very close to each other so that in a few instances tubercles from adjacent rows share a common base. The outer ventrolateral tubercles first appear slightly adapical of the inner ventrolateral tubercles and are spaced somewhat unevenly with a maximum distance of 6 mm between tubercles just adapical of midshaft. The distance between the umblicolateral bullae and the midflank swellings (4.5 mm) is equal to that between the midflank swellings and the inner ventrolateral tubercles, which is much greater than that between the inner and outer ventrolateral tubercles (3 mm) (fig. 22). No ribbing is present on the venter.

AMNH 47299 is a fragment of the adapical half of a body chamber with the umbilical area worn away (fig. 19H–K). It is presumably a macroconch. The ornament is better preserved on the left side and consists of umbilicolateral bullae, midflank swellings, inner and outer ventrolateral tubercles, and prorsiradiate ribs. There are three concave umbilicolateral bullae spaced at approximately equal distances of 4.5–5.5 mm. The most adoral bulla is the most prorsiradiate; the most adapical bulla occurs on a swollen rib, which is convex on the flanks and extends to an inner ventrolateral tubercle. Weak, straight prorsiradiate ribs extend across the midflanks at midshaft. Two swellings occur at midwhorl height, the adapical one of which is linked by a strongly convex rib to an inner ventrolateral tubercle. Both the inner and outer ventrolateral tubercles are equally strong and spaced at approximately equal distances of 5.5–6 mm. The number of tubercles in each row is nearly the same (5 inner and 6 outer ventrolateral tubercles). Each outer ventrolateral tubercle is spaced slightly adapical of the adjacent inner ventrolateral tubercle. The distance between the umbilicolateral bullae and the midflank swellings (5.5 mm) is slightly greater than that between the midflank swellings and the inner ventrolateral tubercles (5 mm), which, in turn, is much greater than that between the inner and outer ventrolateral tubercles (4 mm) (fig. 22). The distance between outer ventrolateral tubercles on either side of the venter is 5.5 mm. There are no ribs on the venter.

AMNH 47290 is the adapical half of a fairly robust body chamber (fig. 19D–G). The whorl section is subquadrate at midshaft; whorl width and height are 12.4 and 17.5 mm, respectively; the ratio of whorl width to height is 0.71. The umbilical wall is steep and convex, becoming more broadly rounded adorally; the umbilical shoulder is fairly abruptly rounded. The inner flanks are broadly rounded, the midflanks are nearly flat and slightly convergent, and the outermost flanks between the inner and outer ventrolateral tubercles are broadly rounded and more steeply convergent. The ventrolateral shoulder is fairly abruptly rounded and the venter is broadly rounded to flat.

The ornament is different on the right and left side. The left side bears four rows of tubercles with only a single row of two weak midflank tubercles on the adoral half of the specimen. In contrast, there are five rows of tubercles on the right side, including two rows of midflank tubercles on either side of midwhorl height. The more dorsal row, which more nearly corresponds to the midflank row on the left side, consists of three tubercles, one very weak and two slightly stronger, spaced at distances of 3.5 mm on the adoral end of the specimen. The more ventral row consists of five tubercles, which are as strong as the strongest tubercles in the more dorsal row, and are spaced at equal distances of 4 mm on nearly the entire specimen. Four umbilicolateral bullae are present on the right side with a spacing of 5 mm between consecutive bullae at midshaft. The inner and outer ventrolateral tubercles are slightly weaker than the umbilicolateral bullae but stronger than the midflank tubercles. There are six inner ventrolateral tubercles evenly spaced at distances of 4.75 mm on the right side. As shown on the left side (there is some erosion on the right side), the outer ventrolateral tubercles are as strong as the inner ones; they are spaced at distances of 3.75–5 mm.

MICROCONCH DESCRIPTION: Paratype AMNH 47297 is the adapical two­thirds of a body chamber of a flat­sided specimen missing part of the venter on the adapical end (fig. 19T–W). The whorl width and height at midshaft are 9.1 and 14.6 mm, respectively; the ratio of whorl width to height is 0.62. The umbilical wall is steep and sharply convex on the adapical part, becoming more broadly rounded and inclined outward at midshaft. Likewise, the umbilical shoulder becomes less abruptly rounded adorally. The midflanks are nearly flat to weakly concave and slightly convergent and the outer flanks between the inner and outer ventrolateral tubercles are more broadly rounded and more steeply convergent. The ventrolateral shoul­ der is fairly abruptly rounded and the venter is nearly flat.

The flanks are ornamented with swollen, widely spaced, straight to convex ribs that bear umbilicolateral bullae and inner ventrolateral tubercles. Three umbilicolateral bullae are preserved on the right side with a spacing of 6.5 mm between the two most adoral bullae. The tiny inner ventrolateral tubercles are irregularly distributed, perhaps due to a pathology, with the distance between tubercles equaling 5.5, 10, and 4 mm, as measured in an adoral direction on the right side. The out­ er ventrolateral tubercles are very weak, probably due to poor preservation. They are approximately evenly spaced at distances of 5 mm at midshaft. There are very faint, radial midflank swellings on the adoral half of the specimen on the right side. The distance between the umbilicolateral bullae and midflank swellings (4.75 mm) is equal to that between the midflank swellings and the inner ventrolateral tubercles, which is greater than that between the inner and outer ventrolateral tubercles (2.5 mm) (fig. 22).

Paratype AMNH 47292 is most of the adapical half of a body chamber with part of the inner whorls attached (fig. 19b–e). The whorl section at midshaft is compressed ovoid; the whorl width and height are 11.4 and 16.6 mm, respectively; the ratio of whorl width to height is 0.69. The umbilical wall is steep and sharply convex and the umbilical shoulder is abruptly rounded. The inner flanks are broadly rounded and slightly divergent, the midflanks are nearly flat and slightly convergent, and the outer flanks are broadly rounded and more steeply convergent. The ventrolateral shoulder is fairly abruptly rounded and the venter is broadly rounded.

The flanks are ornamented with slightly swollen, weakly sinuous ribs that change from rectiradiate to prorsiradiate in an adoral direction. Umbilicolateral bullae become stronger and more prorsiradiate adorally and are evenly spaced at distances of approximately 2.5 mm. Ribs bifurcate on the midflanks and develop weak radial swellings. One such swelling is particularly prominent on the adoral end of the specimen on the left side. There are nine inner ventrolateral tubercles on the left side spaced at distances of 3–4.5 mm at midshaft. A row of two very faint swellings occurs just dorsal of the inner ventrolateral row on the right side. Most of the outer ventrolateral tubercles are not preserved, but on the adapical part of the specimen where they are present, they show approximately the same spacing as the inner ventrolateral tubercles—approximately 4 mm between consecutive tubercles just adapical of midshaft. The venter bears two swollen undulations on the adapical part of the specimen connecting outer ventrolateral tubercles on either side of the venter. The distance between the umbilicolateral bullae and the midflank swellings (4 mm) is slightly less than that between the midflank swellings and the inner ventrolateral tubercles (5 mm), which is slightly greater than that between the inner and outer ventrolateral tubercles (4 mm) (fig. 22).

Paratype AMNH 47289 consists of most of a body chamber, presumably of a microconch (fig. 19N–Q). However, the umbilical seam is straight in side view, suggesting that it could equally be an elongate macroconch. The impression of the phragmocone is visible and shows that there was no gap between the phragmocone and the hook. Parts of the dorsal projection and apertural constriction are present. The whorl section at midshaft is compressed ovoid; the whorl width and height are 11.3 and 15.6 mm, respectively; the ratio of whorl width to height is 0.72. The umbilical wall is steep and sharply convex at midshaft, becoming more broadly rounded near the aperture. Likewise, the umbilical shoulder becomes less abruptly rounded adorally. The inner flanks are broadly round­ ed, the midflanks are flat and subparallel, and the outer flanks are broadly rounded. The ventrolateral shoulder is fairly abruptly rounded and the venter is broadly rounded.

Ribs are swollen, widely spaced, prorsiradiate, and slightly sinuous on the shaft, becoming narrower, more closely spaced, more prorsiradiate, and straighter on the hook. Umbilicolateral bullae are approximately evenly spaced at distances of 3.5 mm at midshaft. As shown on the right side, the bullae become more closely spaced and weaken toward the aperture. On the adoral half of the shaft and hook, there are ten very weak, radial midflank swellings that persist to the aperture; they are evenly spaced on the hook at distances of 1–1.5 mm. The inner ventrolateral tubercles, of which there are 15 preserved on the left side, are much stronger than the midflank swellings. They become more closely spaced, weaker, and smaller toward the aperture. The distances between tubercles at midshaft and at the aperture are 5 and 1.5 mm, respectively. The tubercles occur on ribs on both the shaft and hook but the ribs tend to efface at midwhorl height on the shaft, giving the impression that the tubercles are not linked to the ribs, although they retain an elongate shape. The outer ventrolateral tubercles are similar to the inner ones and are only preserved on the adapical end of the specimen and on the hook. On the adapical end of the specimen, they are large and widely spaced (3.5–5 mm apart) and become smaller and more closely spaced (2– 2.5 mm apart) on the hook. They occur on ribs linking the inner ventrolateral tubercles. The distance between the umbilicolateral bullae and the midflank swellings (3.75 mm) is less than that between the midflank swellings and the inner ventrolateral tubercles (5 mm), which is greater than that between the inner and outer ventrolateral tubercles (3.5 mm) (fig. 22). The distance between outer ventrolateral tubercles on either side of the venter at midshaft is 6 mm. There are weak, straight ribs on the venter just adapical of the aperture.

There are two other fragments of microconchs that help to further amplify the description of the species. AMNH 47294 is part of a phragmocone and adapical half of a body chamber (fig. 19L, M). The left side is completely worn away. The umbilical diameter at the base of the body chamber is 3.3 mm. The whorl section is compressed ovoid. The umbilical wall is vertical and flat and the umbilical shoulder is sharply round­ ed. The inner flanks are broadly rounded, the midflanks are flat and subparallel, and the outermost flanks are broadly rounded and convergent. The ventrolateral shoulder is fairly sharply rounded and the venter is flat. The whorl section is similar at midshaft with a steeply convex umbilical wall.

The phragmocone is covered with slightly sinuous, prorsiradiate ribs. They are straight on the outermost flanks where they intercalate and branch, and straight on the venter with approximately 11 ribs/cm. Each rib bears a tiny outer ventrolateral tubercle. The distances between tubercles at the adapical (broken) and adoral end of the phragmocone are 1 and 1.5 mm, respectively. The row of inner ventrolateral tubercles is not as well defined as the row of outer ones. On the adapical portion of the body chamber, ribs are slightly concave on the outer half of the flanks, and they link inner and outer ventrolateral tubercles; ribs do not occur on the venter. Just adapical of midshaft, ribs are slightly concave on the inner flanks, where they develop into umbilicolateral bullae, and convex on the outer flanks, where they bear weak midflank swellings. The umbilicolateral bullae are initially slightly arcuate and become stronger, straighter, and more prorsiradiate adorally; they are evenly spaced at distances of 2–3 mm. Two radial midflank swellings occur on the adoral end of the body chamber fragment spaced 2.5 mm apart. Inner ventrolateral tubercles are faint and elongate on the adapical part of the body chamber but become stronger, more radial, and more widely spaced adorally, with a distance of 2.25 mm between the two most adoral tubercles. Outer ventrolateral tubercles are present on the entire piece of body chamber and gradually become more widely spaced adorally with a distance of 2.0 mm between consecutive tubercles on the adoral end of the specimen. On the adapical part of the body chamber, outer ventrolateral tubercles are linked to inner ventrolateral tubercles by prorsiradiate ribs, but on the adoral part, out­ er ventrolateral tubercles occur in the gaps between inner ventrolateral tubercles. The distance between the umbilicolateral bullae and the midflank swellings (4 mm) is equal to that between the midflank swellings and the inner ventrolateral tubercles, which is greater than that between the inner and outer ventrolateral tubercles (2 mm) (fig. 22). The last suture at a whorl height of 9.2 mm shows an asymmetrically bifid first lateral lobe (fig. 21B).

AMNH 49426 is most of the shaft of a body chamber (fig. 19X–Z, a). The umbilical shoulder is curved in side view. The whorl section at midshaft is subquadrate; the whorl width and height are 10.6 and 15.2 mm, respectively, in intercostal section, and 11.8 and 15.2 mm, respectively, in costal section; the ratio of whorl width to height is 0.70 in intercostal section and 0.78 in costal section. The umbilical wall is steep and convex and the umbilical shoulder is abruptly rounded. The inner flanks are broadly rounded and slightly divergent, the midflanks are flat and gently convergent, and the outer flanks are broadly rounded and more steeply convergent. The ventrolateral shoulder is fairly abruptly rounded and the venter is broadly rounded.

The flanks are covered with slightly swollen, weakly sinuous, prorsiradiate ribs bearing umbilicolateral bullae and inner ventrolateral tubercles. On the adapical half of the specimen, the sinuosity of the ribs is well expressed; the ribs are concave on the inner flanks and convex on the midflanks. The ribs fade out on the adoral half of the specimen, but this may be due to poor preservation. The umbilicolateral bullae are crescentic and become markedly more prorsiradiate and slightly more widely spaced adorally; the distance between bullae at midshaft is 4 mm. There is a row of faint midflank swellings most of which occur on ribs on the adapical two­thirds of the specimen. The inner ventrolateral tubercles, of which there are six preserved on the left side, are elongated radially and are approximately evenly spaced at distances of 4.5 mm. There are slightly fewer outer ventrolateral tubercles (five of them preserved on the left side) evenly spaced at distances of 4.5–5 mm with the exception of the two most adapical tubercles, which are spaced 7.5 mm apart. The venter is smooth except for one rib near the adoral end of the specimen; it is straight across the venter. The distance between the umbilicolateral bullae and midflank swellings (4.5 mm) is less than that between the midflank swellings and inner ventrolateral tubercles (5 mm), which is greater than that between the inner and outer ventrolateral tubercles (3.5 mm) (fig. 22). The distance between outer ventrolateral tubercles on either side of the venter at midshaft is 5.25 mm.

DIMORPH INDETERMINATE: We describe four specimens that are too fragmentary to determine the dimorph but nevertheless reveal details of the ornamentation. AMNH 47298 is part of a phragmocone with the sutures somewhat corroded (fig. 20A–D). The whorl width and height on the middle of the specimen are 6.7 and 9.8 mm, respectively; the ratio of whorl width to height is 0.68. The whorl section is compressed ovoid with broadly rounded flanks and flat venter. The flanks bear straight prorsiradiate ribs, although they are poorly preserved. On the adapical half of the specimen, the venter is covered with short straight ribs that disappear adorally; there are approximately 10 ribs/cm on the venter based on the average distance between five consecutive ribs. A possible umbilicolateral bulla appears on the adoral end of the specimen. Inner ventrolateral tubercles appear on the adoral oneeighth of the specimen; the distance between tubercles at the adoral end is 2.5 mm. Outer ventrolateral tubercles are present on the entire fragment and become progressively more widely spaced adorally; the distances between tubercles on the adapical and adoral ends are 1 and 3 mm, respectively. The tubercles are mostly paired on either side of the venter and are connected by short ribs on the adapical half of the specimen. The suture at a whorl height of approximately 12 mm is moderately incised and shows a bifid first lateral lobe (fig. 21A).

AMNH 49425 is a fragment of a body chamber with part of the flanks and venter preserved (fig. 20E–H). There are some iridescent patches on the specimen suggesting the presence of a very thin layer of shell. The flanks bear prorsiradiate, slightly swollen, weakly sinuous, fairly widely spaced ribs that terminate in fairly strong inner ventrolateral tubercles, which connect in turn with equally strong outer ventrolateral tubercles. The tubercles in each row are spaced at distances of approximately 3–4 mm; the fragment preserves six tubercles in each row. Two narrow radial swellings occur just dorsal of the inner ventrolateral tubercles on the adoral end of the specimen on the left side, and a single swelling occurs in the same position on the right side.

AMNH 49422 is a fragment of a body chamber with a snail stuck in the adoral end; the left side of the specimen is worn away (fig. 20P, Q). The ornament consists of four rows of sharp tubercles, although the midflank tubercles are elongated radially. The umbilicolateral tubercles are relatively strong and slightly arcuate with steep adapical and more gently sloping adoral sides. They are evenly spaced at distances of 3–4 mm. The midflank tubercles are weaker, thinner, and prorsiradiate; they are evenly spaced at distances of 3–3.5 mm. The inner ventrolateral tubercles are stronger and more conical than the midflank tubercles and are spaced at approximately equal intervals of 4.5 mm. One of these tubercles on the adoral end sits on a sharp prorsiradiate rib. The outer ventrolateral tubercles are slightly weaker than the inner ventrolateral ones but show the same distribution. The distance between the umbilicolateral bullae and midflank tubercles (4.5 mm) is slightly less than that between the midflank tubercles and the inner ventrolateral tubercles (5 mm), which is greater than that between the inner and outer ventrolateral tubercles (4 mm). The distance between ventrolateral tubercles on either side of the venter is 5.5 mm.

AMNH 47285 is the adapical half of a body chamber with most of the umbilical area missing (fig. 20V–Y). The whorl width and height at midshaft are 10.7 and 14.9 mm, respectively; the ratio of whorl width to height is 0.72. The body chamber is ornamented with slightly swollen, weakly sinuous, widely spaced ribs that become progressively more prorsiradiate adorally and bear umbilicolateral bullae and inner ventrolateral tubercles. The umbilicolateral bullae are crescentic and are spaced at distances of 3.5 mm at midshaft. There is a suggestion of midflank swellings. The inner ventrolateral tubercles are approximately evenly spaced at distances of 3.5–4 mm at midshaft. The outer ventrolateral tubercles are smaller but show the same distribution as the inner ventrolateral tubercles, with an outer ventrolateral tubercle generally occurring alongside an inner ventrolateral tubercle.

DISCUSSION: Discoscaphites minardi , n.sp. is very similar to D. iris (figs. 15A, B, G–O, 17A–G). The main differences are (1) the flanks of the body chamber in D. minardi are nearly flat and subparallel, whereas they are usually broadly rounded in D. iris ; (2) the midflank swellings are weak and radial in D. minardi , if they are present at all, whereas they are usually well developed and pointed in D. iris ; and (3) the inner ventrolateral tubercles in D. minardi are radially elongated, whereas they are usually pointed in D. iris .

Discoscaphites minardi also resembles D. conradi in its general shape and ornament (fig. 17N–V). However, the holotype of D. conradi (ANSP 51551) from the Prairie Bluff Chalk, Alabama, illustrated by Jeletzky and Waage (1978: pl. 1, figs. 1–4), is larger and covered with six rows of tubercles. Cobban and Kennedy (1995) characterized D. conradi as a highly variable species, but none of the specimens they illustrated from the Prairie Bluff Chalk of Alabama and Mississippi matches D. minardi . Landman and Waage (1993) stated that macroconchs of D. conradi usually have six to eight rows of tubercles and that microconchs usually have four to seven rows of tubercles; again, however, none of the specimens they illustrated from the Fox Hills Formation of South Dakota matches D. minardi . Specimens of D. conradi from the Severn Formation near Brightseat, Prince Georges County, Maryland, which is only approximately 85 km from the type locality of D. minardi , also bear little resemblance to D. minardi (fig. 17N–V; Kennedy et al., 1997: fig. 20B–J).

In contrast, the specimen called D. conradi ? conradi (Morton) (USNM 250607) figured by Jeletzky and Waage (1978: pl. 3, figs. 16, 17) from the Prairie Bluff Chalk of Alabama is very similar to D. minardi . This fact suggests that a bed­by­bed collection of scaphites from the Prairie Bluff Chalk may reveal D. minardi in the upper beds. In addition, Kennedy and Cobban (1993, fig. 6g –m) documented specimens of D. conradi from the Corsicana Formation of northeast Texas that are slender and some of which are close to D. minardi . However, the outer ventrolateral tubercles in all of these specimens are more closely spaced than the inner ones, whereas in D. minardi the tubercle spacing is approximately the same in both rows.

The Kemp Clay at the top of the Corsicana Formation of northeast Texas contains Discoscaphites roanensis Stephenson, 1941 ( Stephenson, 1941: 428, pl. 90, figs. 1–4), which Jeletzky and Waage (1978) synonymized with D. conradi . The holotype of D. roanensis (USNM 77310), a nearly complete macroconch, is similar to D. minardi in its general form but has three rows of flank tubercles, one of which first appears on the hook. The eight paratypes of D. roanensis are all fragments and comprise parts of the body chambers of three macroconchs and five microconchs. USNM 77311, the figured paratype, is part of the body chamber of a macroconch. It resembles D. minardi in the number of rows of tubercles, but the outer ventrolateral tubercles are more closely spaced that the inner ones.

There are several odd specimens in our collection that we provisionally retain in D. minardi . AMNH 47290 (fig. 19D–G) shows a difference in the number of tubercle rows from one side of the specimen to the other. The left side shows four rows conforming to D. minardi , whereas the right side shows five rows with the two flank rows disposed on either side of midwhorl height, more closely resembling D. conradi . Supernumerary tubercles occur in two other specimens. A single tubercle occurs between the inner and outer ventrolateral rows of tubercles in AMNH 50542 (fig. 18S–U), and two very faint swellings occur in addition to the midflank swellings on the right side just dorsal of the row of inner ventrolateral tubercles in AMNH 47292 (fig. 19b–e). This variation in tubercle number may be due to pathology or may indicate that the number of tubercle rows is not absolutely fixed in this species.

OCCURRENCE: Severn Formation, Kent County, Maryland; upper part of the New Egypt Formation, northeastern Monmouth County, New Jersey (Landman et al., in prep. a). Questionable specimens of this species have also been recovered from the top of the Tinton Formation and as reworked material at the base of the Hornerstown Formation near Freehold, central Monmouth County, New Jersey (Landman et al., in prep. b). This species denotes the D. minardi Zone on the Atlantic Coastal Plain, which represents the middle part of the upper Maastrichtian, corresponding to the upper part of calcareous nannofossil Subzone CC26a and the lower part of Subzone CC26b.

Discoscaphites cf. D. minardi , new species

Figure 15E, F

MATERIAL: A single specimen ( USNM 525324) from the Severn Formation, Round Bay, Anne Arundel County, Maryland.

DESCRIPTION: USNM 525324 is the ventral part of a body chamber approximately 34 mm in diameter with the dorsal part still attached to the matrix (fig. 15E, F). The flanks are broadly rounded to flat, the ventrolateral shoulder is fairly abruptly rounded, and the venter is broadly rounded. The ornament is better preserved on the left side. Broad, rounded, evenly spaced ribs terminate in elongate inner ventrolateral tubercles on the adapical half of the specimen. These tubercles are much more pointed on the right side. The distance between the two most adoral tubercles is 6.5 mm. Midflank tubercles are represented by slight elevations on the broad, rounded ribs. A few outer ventrolateral tubercles are present. Both inner and outer ventrolateral tubercles disappear on the hook, which is ornamented with fine, straight prorsiradiate ribs.

DISCUSSION: The presence of weak midflank tubercles in addition to rows of inner and outer ventrolateral tubercles suggests that this specimen is closely related to Discoscaphites minardi , n.sp. However, it is too incomplete for positive identification.

OCCURRENCE: Severn Formation, Round Bay , Anne Arundel County, Maryland .

Figures

Fig. 16. Discoscaphites gulosus (Morton, 1834), AMNH 50365, macroconch, Peedee Formation, John D. Long County Park, Brunswick County, North Carolina. A, Right lateral; B, ventral; C, left lateral. All figures ×1.

Fig. 15. Ammonites from the upper part of the Severn Formation, Round Bay, presumably on the western shore of the Severn River, Anne Arundel County, Maryland. A, B, G–O. Discoscaphites iris (Conrad, 1858). A, B. USNM 525325, macroconch. A, Ventral; B, left lateral. G, H. USNM 525329, microconch. G, Right lateral; H, ventral. I. USNM 525328, macroconch, right lateral. J, K. USNM 525330, fragment. J, Ventral; K, left lateral. L, M. USMN 525327, microconch. L, Ventral; M, left lateral. N, O. USNM 525326, microconch. N, Right lateral; O, ventral. C, D. Discoscaphites cf. D. iris (Conrad, 1858), USNM 525323, macroconch. C, Left lateral; D, ventral. E, F. Discoscaphites cf. D.

Fig. 18. A–Q, S–Y. Discoscaphites minardi, n.sp., macroconchs, AMNH loc. 3252, Severn Formation, Kent County, Maryland. A–D. Holotype, AMNH 47288. A, Right lateral; B, apertural; C, ventral; D, left lateral. E–G. AMNH 47281. E, Right lateral; F, ventral; G, left lateral. H–K. Paratype, AMNH 47293. H, Right lateral; I, apertural; J, ventral; K, left lateral. L–N. AMNH 47295. L, Right lateral; M, ventral; N, left lateral. O–Q. MAPS A2059a1. O, Apertural; P, ventral; Q, left lateral. S–U. Paratype, AMNH 50542. S, Right lateral; T, ventral; U, left lateral. V–Y. AMNH 47283. V, Right lateral; W, apertural; X, ventral; Y, left lateral. R. Discoscaphites iris (Conrad, 1858), MAPS A2060c1, same loc. as A–Q, S–Y, left lateral. All figures ×1.