276 On some tiext? Species of Ampidlariadce. 



of modern conchologists, of making too many species ; for I 

 have good reason to believe that all the specimens that he has 

 figured, except S. tristensis, (with several varieties in the Bri- 

 tish Museum), belong to one species, for which I propose the 

 name of S. radiata. There is, I believe, another species found 

 in the United States, which Mr. Say has described under the 

 name of Patella altcrnata, which, should my surmises be cor- 

 rect, will be a curious circumstance, as the other two species 

 are confined to the African seas. 



On some new Species of Ampullar iudcc. 

 Marisa intermedia'. 

 M. testa subdiscoidea, laevi, pallide olivacea, lata fusco-uni- 



fasciata; spira concaviusculo-plana, apice subprominente 



acuto; columella (axi) concavo-conica effusa. 



Inhabits Brazils. Mus. J. Sowerby, Nostr. 



Shell nearly discoidal, smooth pale green with a broad 

 brown central spiral band, spire very slightly concave* nearly 

 flat, apex slightly prominent acute, columella (axis) conical 

 concave effused exhibiting most of the whorls ; aperture nar- 

 row, half as broad again as the last whorl but one, peristome 

 simple slightly reflexed in front, axis ii, diameter 1 inch. 



Marisa is the name which I propose for a genus of shells 

 which has been confused with Ampullaria, but which differs 

 from it in having a horny operculum and simple peristome. 



This shell is very interesting as being intermediate between 

 Ampidlaria Comu a?ietis and A. effusa of Lamarck ; and I be- 

 lieve that Mr. Swainson had confounded it with the former 

 species when he observed that Mr. G. B. Sowerby had dis- 

 covered the operculum of that species, for I have reason to think 

 that my specimen is the fellow to the one in Mr. Sowerby's 

 collection, as he presented me with it at the time he bought 

 them; so that the operculum of that species is still a desidera- 

 tum, although I have no doubt that it is furnished with one. 



This shell is instantly to be distinguished from the two 

 former species by the flatness of the spire, and the size of its 

 umbilicus ; and the two specimens that I have seen have only 

 one broad band, whereas the other species have five or six 

 narrow ones, but this may be subject to variations. 



The controversy that has arisen regaining the situation of 

 the M. Comu arietis is an illustration of one of the numerous 

 errors between analogy and affinity ; for there is no more rea- 

 son for placing it amongst the Planorbes on account of its sub- 

 discoidal form, than there would be for arranging the Bats with 

 the Birds on account of their fluttering through the air. As to 



the 



