Coliracemata

Ponder, Winston F., Fukuda, Hiroshi & Hallan, Anders, 2014, A review of the family Clenchiellidae (Mollusca: Caenogastropoda: Truncatelloidea), Zootaxa 3872 (2), pp. 101-153 : 139-140

Coliracemata ? microscopica ( Nevill, 1877)

Figure 27

Valvata (?) microscopica Nevill, 1877: 21 .

Cyclostrema microscopica ; Annandale & Kemp, 1916: 347, fig. 3. Tubiola microscopica ; Annandale, 1924: 858.

Clenchiella microscopica ; Abbott, 1949: 62.

Types and type localities. Holotype: Port Canning (now Canning) (West Bengal, NE India) (Indian Museum, Calcutta, apparently lost, see below). Collected in a brackish water pond about a quarter mile from the river.

Distribution. Known only from the type locality, on the Matla River, NE India.

Description based on Nevill’s (1877: 21, description) and Annandale & Kemp’s (1916, fig. 3) figure.

Shell. Minute (1.5 mm in diameter; Table 3), spire depressed. Protoconch details unknown ( Fig. 27 A, B). Teleoconch of about 2.7 [Nevill says 4 whorls but the figure of the type suggests the number given] convex whorls, surface distinctly sculptured with spiral lirae similar in strength on dorsal and basal surfaces. Periphery apparently evenly convex. Base evenly convex, umbilicus moderately wide (about half width of base). Sutures impressed. Aperture near circular, prosocline, with simple, slightly thickened peristome, no obvious external varix. Colour brownish-red (presumably periostracum only, as is the case with most clenchiellids studied herein), with black deposit.

Operculum. Horny, circular, comparatively rather thick, apparently multispiral.

Head-foot, radula and anatomy unknown.

Remarks. Abbott (1949: 62) stated that a “careful search by the authorities of the Zoological Survey of India failed to bring the types to light”. A letter to one of us (WFP) from Dr N. V. Subba Rao (30 June 1993) confirmed that the type of V. microscopica could not be located and may have been destroyed when some of the mollusc collection was damaged during flooding in 1943. The only figure of a type specimen of microscopica is a drawing of a dorsal and ventral view published by Annandale & Kemp (1916, fig. 3). This clearly shows the narrow umbilicus and fine spiral sculpture that distinguishes this species.

Rao et al. (1993: 156, pl. 1, figs 3, 6) recorded and illustrated a specimen identified as Tubiola microscopica from the Matla River bed, Saimari, West Bengal. The specimen is not a clenchiellid but appears to be a juvenile trochid.

This species is at least superficially similar to Co. mortoni n. sp., Co. clarkae n. sp. and Co.? innocens ( Preston, 1915) (see below).

Figures

FIGURE 27. Coliracemata? microscopica (A, B) modified from the original illustrations by Annandale and Kemp (1916, fig. 3) and Coliracemata? innocens (C – E) modified from the original illustrations by Preston (1915, fig. 9 a – c). Scale bars: 500 µm.