AMPULLARIA Pl. II
1. Subcarinata 2. Nilotica
The politeness of Mr. G. Sowerby has given us the opportunity of examining this rare and little known species, first described and accurately figured by himself. It was discovered, we believe, by Mr. Cranch, the ill-fated naturalist who accompanied the unfortunate expedition to the Congo, in that river. No specimens, we are informed, have subsequently reached this country. The surface is rough, occasioned by irregular corrugated wrinkles: the epidermis olive.
AMPULLARIA subcarinata.
Specific Character.
Shell reverse, thickish; whorls depressed near the suture, and marked by a parallel line; spire short, obtuse; umbilicus large, open, slightly carinated, and marked with an internal groove.
Ampullaria subcarinata. Sow. Genera of Shells, f. 4.
AMPULLARIA Nilotica.
Shell reverse, thin, smooth, whitish, with an Olive epidermis finely striated longitudinally; lower half of the basal whorl much contracted: spire prominent, obtuse; operculum horny; umbilicus large, open, the margin obtusely carinated.
The shell from which our figure was taken we received from Mr. G. Sowerby, under the name of Nilotica, some years ago. Whether it is the same, or specifically distinct from Lamarck's Guinaica, we have no means of judging, otherwise than from the figures he cites of Chemnitz. If these are accurate, there are many points of difference; but no doubt the Editor of the Bulletin des Sciences, will have great pleasure in setting us right upon this subject.
On attentively comparing the descriptions, given by Lamarck, of eleven species of Ampullaria, with those we have characterized in different works, we can only discover two instances wherein the same species have been mentioned by both parties, under different names. Our A. conica, is probably Lamarck's virens, and belongs to the genus Pachystoma, Guild. The other instance is curious; in the Appendix to the Bligh Collection, we described a remarkable variety of A. fasciata, under the sub-specific name of Canaliculata. In the following month appeared the second part of Lamarck's Système, wherein this variety appeared as a species, under the very same name. It would almost appear as if the two accounts had been written at the same moment. We have since had good reason to be confirmed in our suspicion as to this shell being a mere variety of fasciata, from a fine series of specimens sent us from Demerara. We take this opportunity, however, of expressing a belief that our A. leucostoma, is the young shell of rugosa.