Prestonella quadingensis Connolly, 1929

Herbert, D. G., 2007, Revision of the genus Prestonella (Mollusca: Gastropoda: Orthalicoidea: Bulimulidae s. l.), a distinctive component of the African land snail fauna, African Invertebrates 48 (2), pp. 1-19 : 13-14

Prestonella quadingensis Connolly, 1929

Figs 14–16

Prestonella quadingensis: Connolly 1929: 233 , pl. 14, fig. 25; 1939: 293; Bruggen 1985: 292. Type loc.:

‘ Basutoland, Quading’ [= Lesotho, Quthing (Moyeni)], leg. E. Ford.

Description ( Figs 14, 15 ): Extremely similar to P. nuptialis , from which it differs chiefly in the presence of fine, spiral threads on the teleoconch whorls, and axial riblets on the protoconch. The whorls are also perhaps slightly more obese, but ratios of shell proportions overlap extensively with those of P. nuptialis (Table 2). Colour of living animal unknown.

Dimensions: Length up to 12.2 mm, width up to 8.0 mm; adult L/W = 1.43–1.55; body whorl length = 84.9–87.1% of shell length; aperture length = 55.8–64% of shell length (N=4).

Protoconch: Diameter approx. 1.6 mm, comprising approx. 2.0 whorls; basic shape and sculpture similar to that of P. bowkeri ; badly eroded, but retaining traces of strong, widely spaced axial riblets and close-set microscopic spiral striae.

Holotype: LESOTHO: Quthing [Moyeni], leg. E. Ford, ex Farquhar collection, ex Albany Museum ( NMSA J8135 /T2835), length 12.2 mm ( Fig. 14 ).

Paratypes: LESOTHO: ‘ Quading’ leg. E. Ford ( BMNH 1937.12.30.7079-80), two specimens ( Fig. 15 ) .

Additional material examined: LESOTHO: Quthing [Moyeni], leg. E. Ford, e x Albany Museum ( NMSA J8086 ) .

Distribution ( Fig. 16 ): Known only from the type locality in south-western Lesotho, at approx. 1750 m a.s.l.

Habitat: Apart from the fact that the type locality lies at about 1750 m a.s.l., within the grassland biome, nothing is known of the habitat of this species.

Notes: It seems doubtful that this taxon is genuinely distinct from P. nuptialis . In view of the distance between the populations and their probable genetic isolation, some geographical variation in shell form is perhaps to be expected. The axial ribbing on the protoconch of P. quadingensis and its absence in P. nuptialis may not be significant since this character varies considerably between and within P. bowkeri populations. A definitive statement on the validity of this species must await the discovery of additional material for more in-depth study.

Figures

Figs 12–15. Prestonella nuptialis (Melvill & Ponsonby, 1894) and P. quadingensis Connolly, 1932: (12) P. nuptialis holotype, length 11.5 mm (BMNH 1905.1.26.29); (13) undamaged specimen, Cradock, length 13.3 mm (NMSA 1592); (14) P. quadingensis holotype, length 12.2 mm (NMSA J8135/T2835); (15) paratype, length 11.4 mm (BMNH 1937.12.30.7079-80).

Fig. 16. Distribution of Prestonella nuptialis (9) and P. quadingensis ().