Notes on the Pomacea of Surinam, with special reference to Ampullaria sowerbyi Vernhout

During a recent visit to Leyden Museum I was privileged to examine the type of Ampullaria sowerbyi Vernhout (VERNHOUT, 1914, p. 29), preserved in the collection there. This shell, 14 mm in height and 11 mm maximum diameter, is, in my opinion, a typical immature example of Pomacea (Limnopomus) granulosa (Sowerby) (SOWERBY, 1894, p. 49; PAIN, 1949, p. 40). Comparison with other immature granulosa collected in Surinam by Dr. D. C. GEIJSKES leaves no doubt in my mind that they are identical. The noticeable granulose sculpture of P. (L.) granulosa is also present to a lesser extent on most other Limnopomus which I have examined, reduced in some cases, as in P. (L.) columellaris (Gould), so as to be visible only with a strong lens.