Leiosyrinx matsukumai, Bouchet & Sysoev, 2001

Bouchet, P. & Sysoev, A., 2001, Typhlosyrinx - like tropical deep-water turriform gastropods (Mollusca, Gastropoda, Conoidea), Journal of Natural History 35 (11), pp. 1693-1715 : 1708-1710

Leiosyrinx matsukumai n. sp.

(figures 4, 42–48)

Typhlosyrinx supracostata . Matsukuma et al., 1991: pl. 72, figure 7.

Type material. Holotype and six paratypes in MNHN.

Type locality. The Philippines, north of Lubang I., 13°55'N, 120°29'E, 326–330 m [ Musorstom 2, sta. CP 15 ].

Material examined. Taiwan. Tainan, depth unknown, one dd ( NSMT Mo-70638 ex Kawamura collection; Matsukuma et al., 1991: pl. 72, figure 7; this paper, figure 48) . Philippines. Musorstom 1: Sta. 42 , 13°54.5'N, 120°29'E, 379–407 m, one lv (paratype, figures 46-47), one dd. Sta. 43 , 13°51.5'N, 120°28.5'E, 448–484 m, one dd (paratype, figures 44, 45). Musorstom 2: Sta. CP15 , 13°55'N, 120°29'E, 326– 330 m, fou r lv (holotype, figure 42 and one paratype, figure 43). Sta. CP40 , 13°08'N, 122°40'E, 280–440 m, one dd. Musorstom 3: Sta. CP106 , 13°47'N, 120°30'E, 640–668 m, one dd .

Distribution. Taiwan and the Philippines, living at 330–379 m, shells to 640 m.

Description. Holotype (figure 42). Shell rather thin but solid, polished, with high spire occupying 37% of total shell height. Protoconch partly corroded, remaining one whorl light brown, with diagonally cancellated sculpture. Teleoconch whorls eight. F irst two teleoconch whorls sculptured with crenulated subsutural fl ange, resulting in a slightly channelled suture, and three strong spiral cords below subsutural ramp. Remaining whorls with shallow, impressed suture, whorl pro fi le weakly convex, fl attened in adapical half, subsutural ramp very poorly de fi ned, periphery slightly below mid-height, without axial sculpture. Spiral sculpture obsolete on most spire whorls, on last whorl consisting of low cords, very weak and broad on periphery, stronger and more closely set towards canal. Shell base not differentiated from canal. Aperture broad, inner lip evenly curved, covered by thin white callus, with six strongly opisthocline cords on columellar part. Anal sinus deepest at twothirds of the width of the subsutural ramp, moderately deep, rather narrow, outer lip evenly projecting below sinus. Canal short, broad, widely open. Colour light brownish orange, with indistinct lighter band encircling base.

Dimensions: shell height 37.2 mm, last whorl height 21.7 mm, aperture height 17.0 mm, diameter 12.0 mm.

The largest paratype (50.3 ✕16.6 mm, figures 44, 45) has a rather well-de fi ned, narrow, concave subsutural ramp on last whorl, and the suture is somewhat adpressed. The colour pattern is usually indistinct, but fresh specimens have pale banding on the last whorl, one wide light brownish orange band occupying adapical part of whorl and another, of variable width, encircling shell base. Protoconch multispiral, light brown, protoconch I fi nely granulose, diameter ca 250 m m, protoconch II diameter 600 m m, consisting of 1.3–1.8 rather fl at whorls with diagonally cancellated riblets. Radular teeth small, 91 m m in a 35.3 mm high paratype, simple, similar to those of Leiosyrinx immedicata (figure 4).

Remarks. Leiosyrinx matsukumai was illustrated by Matsukuma et al. (1991) under the name Typhlosyrinx supracostata , but it clearly differs from the latter in the complete absence of axial ribs. It co-occurs with it in the Philippines, but the two species occupy different bathymetric ranges, four of five samples of L. matsukumai are in 330–448 m (lv and dd), and L. supracostata is recorded there from one large sample in 856– 884 m. The lack of axial sculpture recalls L. immedicata , from which L. matsukumai differs in the early teleoconch sculpture with crenulated subsutural fl ange, the overall much weaker spiral sculpture, and lighter colour without axial streaks. For differences from L. apheles , see that species.

Etymology. Named after Dr Akihiko Matsukuma, formerly curator at NSMT, now at University of F ukuoka.