Mastonia issa 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 : 75-77

Mastonia issa Jousseaume, 1898

( Fig. 50 )

Mastonia issa Jousseaume, 1898: 74 , not illustrated.

TYPE LOCALITY. — Djibouti.

TYPE MATERIAL. — Lectotype. Djibouti • MNHN-IM-2000-29263; 1 specimen; here designated.

Paralectotype. Djibouti • Triphoridae indet.: MNHN-IM-2000-707; 1 paralectotype .

ORIGINAL DESCRIPTION. — Testa solidula, pyramidalis, elongata , subulata , alba et pallide fulvo zonata; anfr. 16 regulariter crescenti, primi apice olivaeforme instituentes, sequentes carinis granulosis tribus (media minor), cincti, granulae oppositae in seriebus longitudinalibus dispositae, costa postice alba, altera luteo-fulva; sutura canaliculata fusca, anfractus ultimus antice attenuatus, carinis moniliferis quinque ornatus ; apertura subrotundata lateraliter fîssa, canalis parum recurvus. Long. 4mm; diam. 1mm.

[Latin diagnosis followed by a discussion in French]

TRANSLATION OF THE LATIN TEXT. — Rather solid shell, pyramidal, elongated, subulate, with yellow and white bands; 16 regularly growing whorls, first whorls forming an olive-shaped apex, subsequent with three granulated spiral cords (the one in the middle is smaller), the opposing granules are arranged in longitudinal series, the posterior cord is white, others are dark yellow; brown canaliculated suture, the last whorl is posteriorly flattened, adorned by five granular spiral cords; roundish and laterally fissured aperture, slightly curved siphon. Length 4 mm; diameter 1 mm.

DIAGNOSIS. — Shell conical with flat sides. Syntype 5.3 mm high. Teleoconch of 10 whorls. Three spiral cords present, the second appearing on the fifth whorl. First and third cords with tubercles at the intersection with rather orthocline axial ribs. Second cord with flat tubercles becoming larger at the lower whorls. Peristome without additional spiral cords. Posterior sinus shallow. Base with two additional cords of which the first with tubercles, the second smooth. Protoconch paucispiral of 1.5-2 whorls with two rows of large granules, the lower being more prominent.Teleoconch brown; third spiral cord whitish on the lower half. Protoconch brown.

REMARKS. — Lot MNHN-IM-2000-707 contained two specimens belonging to different species. The first specimen ( Fig. 50 A-I) has on most of the teleoconch the three spiral cords described by Jousseaume (“ granulosis tribus ”) and is here designated as lectotype to stabilize the nomenclature. The second specimen ( Fig. 50 J-Q) has three spiral cords only on the last whorl and can be further distinguished by the occurrence of additional spiral cords on the peristome and a brown colour with only the first and second cords of the second last whorl white.

Figures

FIG. 50. — Mastonia issa Jousseaume, 1898, Djibouti: A-I, lectotype, MNHN-IM-2000-29263; front (A, B), side (C, D), back (E), protoconch (F, G), peristome (H, I); J-Q, Triphoridae indet., paralectotype, MNHN-IM-2000-707: front (J, K), side (L, M), back (N), peristome (O, P), microsculpture (Q); R-U, original labels. Scale bars: A-E, 2 mm; F, G, Q, 0.2 mm; H, I, O, P, 0.5 mm; J-N, 1 mm.