Cerithium (Triforis) levukense Watson, 1880

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

Cerithium (Triforis) levukense Watson, 1880

Figure 116

Cerithium (Triforis) levukense Watson 1880: 100, not illustrated. Illustration available in Watson (1886): 551, pl. XXIX, fig. 4.

Type locality.

"Levuka, Fiji".

Type material.

Syntypes: NHMUK 1887.2.9.1760-1: 2 specimens, type locality .

Original description.

July 29, 1874. Levuka, Fiji. 12 fms.

Shell.- Sinistral, sharply conical, with a narrow and produced base, solid, yellowish white, glossy. Sculpture. Longitudinals.- there are (on the last whorl) about twenty longitudinal rows of round tubercles, which rows form a small rib across the whorl, and are more or less continuous up the spire; these continue on the base as strongly as on the upper part of the whorls. These rows are parted by shallow rounded depressions. Spirals-the longitudinal rows are cut by narrow little rounded grooves, whose intersection with them forms the tubercles. On the upper whorls there is only one such spiral groove, so that there are only two tubercled spirals, but the groove gradually widens, and there appears in the bottom of it a minute additional spiral, which finally becomes as large as the other two; on the base are 3 equally divided tubercled spiral threads, of which the inmost is the smallest, and it ceases at the siphonal tube. The apex consists of 6 small rather elongated narrow whorls, of which the first 1½ have about ten rows of minute tubercles faintly connected by spirals; the next 4½ whorls are crossed by about 24 longitudinal sharp little ribs, rising into points at the carina, which is a continuous spiral thread. This carina on the first of these whorls is near the base, but later it rises so as to encircle the upper part of the whorl. The minute spiral rows of tubercles, which alone appear on the first whorl and half, cover the whole surface (both ribs and interstices) on the later apical whorls. The regular sculpture does not begin abruptly and at once, but a tongue of this new sculpture breaks across the top of the whorl, while the lower part retains the earlier ornamentation. Colour. The apical whorls are amber, the rest of the shell yellowish white, with a narrow amber-coloured thread within the contraction of the base of each whorl; this spiral thread is not continuous, being interrupted by each of the longitudinal rows of tubercles. Spire high, sharply conical, with a very slight convexity in its lines of profile, which are not perfectly alike. Apex a narrow and perfect cone, ending in a small rounded point. Whorls 17, of very regular increase, flat on the side; the whole last whorl is contracted and a little elongated; the base is narrow and flat. Suture sharply impressed, and broader than the spiral grooves, being marginated on its upperside by a minute flat surface, which runs round the base of the superior whorl. Mouth almost more than perpendicular, square, with a largish auricle at its upper corner, and a small and very transverse rift at the pillar. Outer lip sharp, thin, straight, perpendicular, angulated at the basal corner, flat across the base, turned in towards the mouth and pinched in at the pillar, where it joins the pillar-lip, closing in the side of the small siphonal canal, whose edge is sharp and straight, or a very little contracted all round. Pillar straight in front, then very much bent back, so that its posterior line almost stands on the edge of the base. Pillar-lip expanded but abruptly defined on the base, blunt but projecting on the pillar, where it is covered by and cemented to the outer lip. H. 0.22. B. 0.075 least 0.06. Penultimate whorl 0.032. Mouth, length 0.037, breadth 0.035. This beautiful little species is very like in general aspect to C. perversum, L.; but, apart from other obvious differences, the sculpture of the apex is quite distinct. In that species the extreme apex has about seven spiral scatches, parted by roughened threads, and the following whorls are beset with much closer-set and more numerous riblets, and they have two close-set spirals at the carina. The whole of this sculptured apex (in C. perversum) is stumpier, and the whorls are not so angulated, and the extreme point is blunter. T. Hindsii, Desh. (Bourbon Moll. p. 99), is very near, but is less contracted in front towards the base, has not there near the mouth four rows of pearls, has the pearls white on a brown ground, has not the single amber thread, and is a little narrower in proportion.

Diagnosis.

The adult syntype is 4.4 mm high. Shell cyrtoconoid with flat whorls. Teleoconch with at least 11 whorls, but the apical part is missing. Three spiral cords are present with the second developing initially as a narrow thread and attaining full size only on the last whorl. A fourth smooth suprasutural cord is visible. Peristome incomplete in the adult syntype. Siphonal canal short. Base flat, with two weakly sculptured spiral cords. Protoconch present only in the juvenile syntype and likely multispiral as illustrated by Watson. Teleoconch light yellowish with a narrow orange-brown line on the lower part of the third spiral cord.

Figures

Figure 116. Cerithium (Triforis) levukense Watson, 1880, Levuka, Fiji. A, G Original figure. B-E, H, I Syntype NHMUK 1887.2.9.1760: front (B, C), side (D, E), aperture (H), peristome (I). F Syntype NHMUK 1887.2.9.1761: front. J Original labels. Scale bars: B-F: 0.5 mm; H: 0.3 mm.