by William Swainson

“ 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. ”

“ 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. ”