Triforis dolicha Watson, 1886

Albano, Paolo G., Bakker, Piet A. J. & Sabelli, Bruno, 2019, Annotated catalogue of the types of Triphoridae (Mollusca, Gastropoda) in the Natural History Museum of the United Kingdom, London, Zoosystematics and Evolution 95 (1), pp. 161-308 : 161

Triforis dolicha Watson, 1886

Figure 114

Triforis dolicha Watson (1886): 565-566, pl. XLII, fig. 1.

Type locality.

"Lat. 9°59'S, long. 139°42'E West of Cape York, North-east Australia"

Type material.

Syntypes: NHMUK 1887.2.9.1767: 1 specimen, type locality .

Original description.

Station 188. September 10, 1874. Lat. 9°59'S., long. 139°42'E. West of Cape York, North-east Australia. 28 fathoms. Green mud.

Shell.- Long and narrow, conical, pale, spotted with brown, with three rows of fine tubercles on the later whorls and two on the earlier, a furrowed suture, a small regularly tapering apex, and a square barely produced base. Sculpture: Longitudinals-there are on each whorl about 16 riblets, which originate at the upper row of tubercles, and swell down to the lower; they are parted from each other by little shallow pits, and they but feebly and doubtfully run down the spire, being not quite coincident in the adjoining whorls, and being parted by the sutural furrow; near the outer lip the riblets subside into continuous bars, which are prolonged to the base. Spirals-on the last four whorls there are three, on the earlier two, rows of tubercles set upon the longitudinals, and slightly connected in each row by a fine thread; round the angle of the base runs a sharp rounded thread; at the top of the pillar is another finer; on the pillar itself there are two folds. Colour pale brownish, with darker stains. Spire high and narrow, conical. Apex conical, consisting of five rather sharply angulated and carinated whorls, which are ornamented by minute not quite regular longitudinal bars; the extreme tip is small, rounded, quite smooth, polished, and not very prominent, but rather spread out than immersed. Whorls: there are 11½ regular whorls, which are short and of very gradual increase; the edge of the base is bevelled off, but the base itself is flat, with a slight hollowing in the middle. Suture furrowed, but in itself invisible, rather oblique. Mouth somewhat squarely rounded, small, bluntly pointed above. Outer lip is very thin and sharp; has at its insertion a small deep rounded sinus, below which it advances very much into a scoop-like form on the base, and is on the right sharply bent in upon the pillar, the forward edge of which it inwraps. Pillar very short indeed; its point is twisted, and very sharply bent to the right, infolding the generic canal. Inner lip concave, very short, with a thickened edge; there is a minute nick at its junction, with the outer lip on the pillar. H. 0.184 in. B. 0.048. Mouth, height 0.027, breadth 0.022. Apex, height 0.018, breadth 0.013.

This species is not at all unlike the smaller forms of Triforis perversa (Linne), of Europe; but, besides very many minute points of distinction, the base is squarer, with two not three threads, the labral sinus is much deeper, the mouth is rounder, the basal lip more produced, and the pillar tip more bent and elongated; the sutural furrow, too, is deeper, wider, and less oblique, and while the apex is slightly broader, the extreme tip is a very little smaller.

Diagnosis.

Syntype 4.3 mm high. Shell slightly cyrtoconoid with flat whorls. Teleoconch of 11 whorls with three spiral cords, the second as a narrow thread until the last whorl, with tubercles at the intersection with the prosocline axial ribs. A fourth smooth suprasutural cord is visible in the second half of the shell. Numerous prosocline growth lines are visible in the interspaces between the cords. Peristome with a shallow posterior sinus and additional spiral cords. Siphonal canal long. Base rather flat and concave with two additional smooth spiral cords. Protoconch incomplete in the syntype, but clearly multispiral with at least four whorls. The last three bear a single strong spiral keel and axial riblets. Teleoconch apparently whitish, but the syntype is worn; the "darker stains" described by Watson may be again due to taphonomic damage. Protoconch light brown.

Figures

Figure 114. Triforis dolicha Watson, 1886, West of Cape York, North-East Australia. A Original figure. B-H, J, K Syntype NHMUK 1887.2.9.1767: front (B, C), side (D, E), back (F), protoconch (G, H), peristome (J, K). I Original labels. Scale bars: B-F: 0.5 mm; G, H: 0.1 mm; J, K: 0.2 mm.