Crenilabium pacificus Kuroda & Habe

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 597-599

Crenilabium pacificus Kuroda & Habe in Habe, 1961

Figs 4A-E, 5

Crenilabium pacificus Kuroda & Habe in Habe, 1961: 87, pl. 42, fig. 11.

TYPE MATERIAL. — Probable holotype NSMT Mo 38661 .

TYPE LOCALITY. — Off Choshi , central Honshu, Japan, 100-150 m.

MATERIAL EXAMINED. — Philippines. ESTASE 2: stn CP 2, 14°05‘N, 120°02‘E, 2050 m, 2 dd .

North of New Caledonia. BATHUS 4: stn DW 914, Grand Passage, 18°49’S, 163°15’E, 600-616 m, 1 dd (Figs 4B, C).

New Caledonia proper. BIOCAL: stn DW 77, 22°15’S, 167°15’E, 440 m, 1 dd.

Loyalty Ridge. BIOGEOCAL: stn CP 232, 21°34’S, 166°27’E,

760-790 m, 1 lv, shell destroyed to dissect radula (Figs 4D, E).

Fiji. BORDAU 1: stn CP 1398, 16°22’S, 179°56’W, 907-912 m, 1 dd; stn DW 1488, 19°01’S, 178°25’W, 500-516 m, 1 dd.

Tonga. BORDAU 2: stn DW 1531, Eua, 21°12’S, 174°56’W, 970-983 m, 1 dd (Fig. 4A); stn DW 1552, S of Nomuka Islands, 20°38’S, 174°58’W, 491-500 m, 1 dd.

DISTRIBUTION. — Originally described from the Sea of Kashima-nada , Pacific coast of Japan, and subsequently cited from the Japan Sea , in 100-300 m (Hori 2000a). Records herein from the Philippines, New Caledonia, Loyalty Ridge, Fiji and Tonga (Fig. 5), in 440-2050 m, live in 760-790 m.

DESCRIPTION. — Shell morphology. Length 9 mm, width 3.5 mm (largest specimen examined). Shell solid, very elongate (Fig. 4A). Body whorl short, about 1/2 the shell length; spire conical, very elongate, with 3-4 whorls. Suture

FIG. 4. Shell morphology and anatomy of species of Crenilabium Cossmann, 1889 and Obrussena Iredale, 1930 . A, Crenilabium pacificus Kuroda & Habe, 1958 , (9 mm), ventral view, Tonga, BORDAU 2 stn DW 1531; B, protoconch, New Caledonia, BATHUS 4 stn DW 914, scale bar = 500 Μm; C, same shell, sculpture, scale bar = 100 Μm; D, radula, New Caledonia, BIOGEOCAL stn CP 232, scale bar = 20 Μm; E, same specimen,jaws,scale bar = 20 Μm. F, Obrussena bracteata (Iredale,1925) ,(6 mm),ventral view, Tonga, BORDAU 2 stn DW 1549; G, same shell, protoconch, scale bar = 300 Μm; H, same shell, sculpture, scale bar = 300 Μm; I, radula, Tonga, BORDAU 2 stn DW 1554, scale bar = 20 Μm.

narrowly channeled. Protoconch globose, about 1 whorl and 500 Μm in diameter (Fig. 4B). Umbilicus closed. Aperture wide and short, about 1/2 the body whorl. Columellar margin simple, with no denticles. Sculpture of a few irregular spiral grooves (Fig. 4C). The grooves are separated by gaps about as wide as the grooves themselves. Colour uniformly whitish.

Anatomy. The radular formula is 23 x 28.0. 28 in a specimen from New Caledonia (BIOGEOCAL stn CP 232). The radular teeth are all similar in shape and size (Fig. 4D). The teeth have a central, long, narrow cusp with 2 elongate denticles. The jaw is composed of several elements with a central, pointed, robust cusp and a short denticle on each side (Fig. 4E).

REMARKS. — Kuroda & Habe in Habe (1961) described Crenilabium pacificus as the first species of the genus from the Pacific Ocean and different from the Atlantic species Crenilabium exilis (Jeffreys, 1870) . The material here examined has a similar shell morphology to that of specimens from Japan illustrated by Hori (2000a) and they are included in the same species.

The radula of Crenilabium pacificus differs from that of Crenilabium exilis , described by Bouchet (1975), in lacking a rachidian tooth and having denticulate lateral teeth. Bouchet (1975) based his diagnosis of Crenilabium on the anatomy of C. exilis , so this diagnosis has to be modified to accommodate the features of C. pacificus . Crenilabium pacificus is here maintained in Crenilabium because of its shell morphology.