Clathrocaspia pallasii (Clessin & W. Dybowski in W. Dybowski, 1887)

Fig. 12 a–h, m–p, r, s

Caspia Pallasii nob.—Clessin & W. Dybowski in W. Dybowski 1887: 37.

Caspia Pallasii n. sp. —W. Dybowski 1888: 79, pl. 3, fig. 3a, b.

Clathrocaspia pallasi [sic] (Dyb.)— Kolesnikov 1947: 108, 111.

Pyrgula (Caspia) pallasii (Cless. & W. Dyb.) — Logvinenko & Starobogatov 1969: 378, fig. 3675).

Pyrgula (Caspia) sowinskyi Logv. et Star. sp. n. — Logvinenko & Starobogatov 1969: 378, fig. 3674). [partim, without figure] Pyrgula pallasii (Clessin et W. Dybowski in W. Dybowski, 1888)— Kantor & Sysoev 2006: 101–102, pl. 45, fig. N.

Pyrgula sowinskyi Logvinenko et Starobogatov, 1968 — Kantor & Sysoev 2006: 104 [partim, without figure]

Clathrocaspia pallasii (Clessin & Dybowski in Dybowski, 1887)— Wesselingh et al. 2019: 72.

Caspia (Clathrocaspia) pallasii Clessin & W. Dybowski in W. Dybowski, 1887 — Anistratenko et al. 2019: 40, fig. 2J–P.

Type material. Lectotype (ZB-M W.Dyb. 104) and 67 paralectotypes (ZB-M W.Dyb. 5, 74, 104 and 105) (designated by Anistratenko et al. 2019).

Type locality. “Kaspi-See” (Caspian Sea, without further details; Table 1, locality 26).

Other material. 16 shells in ZIN collection of Starobogatov collected off Cheleken Peninsula (locality 16). In addition, a part of the type material of C. isseli (localities 14, 21) and Pyrgula sowinskyi (locality 24) belong to C. pallasii (see discussion under C. isseli and C. gmelini above). Also, the material includes several specimens from the Middle Caspian Basin (locality 9), labelled as “ paratypes ” of “ Caspia microcingulifera ”, an unavailable collection name coined by Starobogatov (ZIN, no number).

Description. Slender elongate shell, with 5 poorly convex, sometimes slightly stepped whorls. Protoconch large, bulbous, measuring c. 1.3 whorls and c. 420–430 µm in diameter (Fig. 12o, p, r, s). Teleoconch sculpture consists of fine to prominent reticulum, whereas spiral keels are more prominent in most specimens. Last whorl comparably small, often compressed. Base low, aperture small and broadly ovoid, often laterally slightly expanded; umbilicus absent or very narrow.

Remarks. A certain variability in shell elongation, whorl convexity and sculpture expression is evident among the type series (Fig. 12 a–e). The typical features of C. pallasii are the slender elongate shell, the poorly convex whorl and the large, bulbous protoconch (Fig. 12o, p, r, s), which distinguish the species from C. isseli and C. gmelinii . These typical features are also found in at least one paratype of P. sowinskyi (Fig. 12m, n); this specimen is considered to belong in C. pallasii .

Finally, the ZIN collection of Starobogatov contains a “ holotype ” and 12 “ paratypes ” of “ Caspia microcingulifera ”, an unavailable collection name. A part of the material, which was collected in the middle Caspian Sea (localities 6, 9), closely resembles Clathrocaspia pallasii (Fig. 12f) and is referred to this species here. The so-called “ holotype ” and at least one of the “ paratypes ” do not belong to C. pallasii; they are discussed under the chapter dealing with doubtful names below.

Distribution. Endemic to the Caspian Sea, reported from water depths between 50 and 150 m (Logvinenko & Starobogatov 1969). Tarasov (1996b) mentioned this species from 311– 870 m. No living specimens of C. pallasii have ever been found.