Caecum subquadratum Carpenter, 1859

Figs 1A–I, 3, 21E, 22A–C, 23A–C, 26G–I

Caecum subquadratum Carpenter, 1859: 433 .

Caecum subquadratum: Tryon 1886: 216 .

Caecum subquadratum: Hedley 1914: 293, pl. 18, fig. 67.

Caecum subquadratum: Pizzini & Raines 2011: 28, fig. 3H.

Type locality: SOUTH AFRICA: Port Elizabeth, here amended (see under remarks) .

Type material examined: Lectotype herein selected (NHMUK 1858.12.9.13, Fig. 21E), glued on a small glass slide labelled by the author with white ink and a paper label, specifying the origin from Bean’s colln (Fig. 21F).

Material examined: SOUTH AFRICA: Western Cape: 4 lv and 35 sh, Langebaan Lagoon, Saldanha Bay, xii.1987 (JPM) ; 1 lv and 4 sh (1 juv), Saldanha Bay, Langebaan Lagoon, grit washed up on sandy beach, leg. J.P. Marais xii.1987 (NMSA E1489) ; 1 lv and 1 sh, Hermanus (between False Bay and Cape Agulhas), v.1990 (JPM) ; 1 lv with operculum in a small glass vial, Walker’s Bay, W of Knysna, iii.1991 (JPM) ; 1 lv and 1 sh, Walker’s Point, W of Knysna, leg. J.P. Marais iii.1991 (NMSA S3729) ; KwaZulu-Natal: 1 sh, Leisure Bay, Port Edward, beach, iii.1986 (JPM) .

Original description: “33? Caecum subquadratum, n. s.

? Caecum (Fartulum) t. elongata, minima, laevi, haud nitente; apertura haud contracta; septo submamillato, subungulato; margine laterali extante, supra satis convexo, lateribus rectis, parallelis; apice obtusissimo, lato, ad latus quadrato: operculo? ... Long..068, lat..009–.012”

Additional description: Tube cylindrical, slender, slightly arched, whitish to transparent, in beached specimens often with alternating white and semitransparent bands, without sculpture. Aperture simple, sometimes with a barely visible swelling. Surface dull, smooth, featureless. Septum opaque, dome-shaped, very protruding. Mucro nail-like, rotated toward the right side, as high as the septum. When viewed from the right side the septum shows a subquadrate outline, while in ventral view it is bigibbous. Periostracum colourless. Juveniles are similar to the adults, and are distinguished by the subcylindrical and more arched tube, and by the less protruding septum and proportionally higher mucro which shows a more rounded lateral outline. Larval stage unknown. Operculum thin, corneous, circular, multispiral, composed of a central nucleus surrounded by a tight spiral of 4–5 whorls. External side slightly concave, internal side with a raised central disk (Fig. 1C).

Length: 1.6–1.9 mm.

Distribution: Southwestern to eastern coast of South Africa, from Saldanha to Port Edward (Fig. 3).

Remarks:Although the type locality of this species seems to be clearly indicated, i.e. Port Elizabeth, both the synopsis at the end of Carpenter’s paper (1859: 443) and the original label of the lectotype refer to Australia (Fig. 21F). However, there is no toponym that refers to a Port Elizabeth in Australia. Conversely, a well-known Port Elizabeth exists in South Africa, hence one can suspect some confusion by Carpenter. Nevertheless in the introduction of his paper, Carpenter (1858: 417) clearly states that he could not find any Caecum species “at the Cape, or at Port Natal [today Durban]”, so one can deduce that he did not examine any Caecidae from South Africa. Moreover, C. subquadratum is the only Australian species reported in his paper. This ambiguity was also noticed by Hedley (1914), who reported a drawing of the lectotype but no Australian records. Furthermore, there is no specimen in either the AMS or WAM collections ascribable to subquadratum . Despite the uncertainty of the type locality, C. subquadratum is a welldefined species, characterized by a slender, cylindrical tube and by the squared profile of the septum in lateral view, while in ventral view it is more or less bimamillated. South African specimens perfectly fit the lectotype, except for the length of the tube. In fact, some populations are notably longer than the lectotype, suggesting that it is a subadult shell. On the basis of the available information the type locality of C. subquadratum is here amended as: SOUTH AFRICA: Port Elizabeth.