Obesula mus Jousseaume, 1898

Albano, Paolo G., Franco, Davide Di, Azzarone, Michele, J., Piet A., Bakker & Sabelli, Bruno, 2023, Review of the types of Indo-Pacific Triphoridae (Mollusca, Gastropoda) in the Muséum national d’Histoire naturelle, Paris, Zoosystema 45 (2), pp. 13-106 : 83

Obesula mus Jousseaume, 1898

( Fig. 56 )

Obesula mus Jousseaume, 1898: 76 , not illustrated.

TYPE LOCALITY. — Djibouti.

TYPE MATERIAL. — Syntypes. Djibouti • MNHN-IM-2000-1595; 2 specimens; Djibouti .

ORIGINAL DESCRIPTION. — Testa solidiuscula cylindraceo ovata, apice attenuata, longe acuminata, lutea, costis tenuis granulosis ornata; anfr. 15 irregulariter crescenti, sutura parum distincta separati, primi 4 nigri, sequentes costis 3 granulosis, inaequalibus (media parum minuta) cincti, ultimus antice attenuatus, subrotundatus, costis granulosis quinque rugatus; intercostas anteriores et penultima linea fulva decurrans; apertura pyriformis linea nigra pictaurata; canalis brevissimus. Long, 4mm 2; diam. 1mm 2.

[Latin diagnosis followed by a discussion in French]

TRANSLATION OF THE LATIN TEXT. — Slightly solid, ovate and cylindrical shell, slender apex, very acute, yellow, adorned by thin granular spiral cords; 15 irregularly growing whorls, separated by a slightly distinct suture, first four whorls are brown, subsequent whorls with three unequal granular spiral cords (median whorl slightly smaller), anteriorly reduced last whorl, roundish, with five granular spiral cords; anterior and penultimate interspaces with a brown line; pyriform aperture with a brown line; very short siphon. Length, 4.2 mm; diameter 1.2 mm.

DIAGNOSIS. — Shell cyrtoconoid. Illustrated syntype 4.6 mm high. Teleoconch of 11 whorls. Three spiral cords present, the second appearing on the seventh whorl. First and third cords with tubercles at the intersection with rather orthocline axial ribs. Tubercles on the first spiral cord larger. Second cord initially with flat tubercles becoming larger on the lower whorls. Spiral microsculpture of fine threads between the spiral cords. Posterior sinus shallow. Peristome rebuilt after breakage in the syntype and thus not reliable to assess the presence of additional spiral cords. Base with two spiral cords of which the first developing tubercles, the second smooth. Incomplete protoconch in the syntype, but clearly multispiral with two spiral keels and axial riblets. First two teleoconch whorls white, others yellowish to light brown with a brown line running between the second and third spiral cords. Protoconch brown.

Figures

FIG. 56. — Obesula mus Jousseaume, 1898, Djibouti: A-I, syntype, MNHN-IM-2000-1595 front (A, B), side (C, D), back (E), protoconch (F, G), peristome (H), microsculpture (I); J-L, original labels. Scale bars: A-E, 1 mm; F, G, 0.1 mm; H, 0.5 mm; I, 0.2 mm.