PLANORBIS. 



117 



Fiff. 195. 



Planorbis trivolvis. 



Planorhis irivolris, var. f'lUiix, IIai.demax, Mon. 15, pi. iii, f. 1-3 (1844). 

 Planorbis hntus, Goulp, Jnv. 202, f. 132 (1841). 

 Helix trivolvis, Eaton, Zool. Text-Book, 194 (182C). 

 Cochlea irium orhum, Lister, Couch, pi. 'cxl, f. 4(J. — Petiver, Gazopliyl. 

 pi. cvi, f. IG. 



This species probably inhabits all of the United States and 

 Canada. It has been found at Fort Simpson, to the lied River 

 of Louisiana, from Puget Sound to San Diego, 

 in Utah, and from New England through the 

 Western and Middle States. Poey cata- 

 logues it among the Cuban sCells. 



Fig. 195 is a better I'epresentation of the 

 species than the fac-simile of Mr. Say's 

 figure given in Fig. 104. 



I give below the original descriptions of 

 the synonyms of this species. Of these 

 Physa planorhuJa, Bulla Jluviatilis, and 

 Planorbis regidaris are immature forms. 

 Plan, megasloma and Plan, macrosiomus 

 are an overgrown form or monstrosity. All 

 the following figures are fac-similes except- 

 ing Fig. 19G, which was drawn from the original specimen of Mr. 

 Lea. 



Haldeman quotes PL regularis as a synonym, and Adams PL 

 lentus and corpulentus. 



Planorbis regularis, Lea. — Shell siibglobo.se, above nearly flat, beneath 

 narrow, umbilicate, pellucid, pale yellow, obsoletely striate ; whiris three, 

 above carinate ; lip acute, margined, within thickened ; aper- 

 ture ovate. 



Hab. United States. My cabinet, and cabinet of P. H. 

 Nicklin. Diam. .30, length .20 of an inch. 



I have unfortunately mislaid the label which accompanied 

 the shells from which the above descriptions were made. My 

 impression is that they came from one of the Western States. 

 All the specimens before me are very much alike in size and 

 form — being exceedingly regular. The striae are more percep- 

 tible around the umbilicus and on the spire. On the side they 

 are so miach obliterated as to permit the whirl to present a 

 shining appearance. The carina is very sharp and well defined. 

 It has very much the appearance of a young trivolvis, Say, and may possibly 

 be only a variety of that species. {Lea.) 



