PLANORBIS. 



133 



tus, IS readily distinguished from all other American species by the re- 

 volving hairy lines. It is the analogue of the European P. albus, from 

 which it is difficult to designate any very characteristic difference. It is, 

 however, a thinner shell, the last whirl increasing more rapidly ; and it 

 maintains its yellowish-horn-color, whereas P. albus assumes a spermaceti 

 or still whiter appearance. The Ihies, too, disappear more entirely when 

 the epidermis is gone. {Gould. — P. hirsutus.) 



Planorbis albus, Mijller, Haldeman, Mon. 29, pi. iv, f. 8-10 (1844). 



Planorbis hirsutus, Gould, Am. Journ. Sc. [i], XXXVIII, 196 (1840) ; 

 Invert, of Mass. 206, f. 135 (1841) ; Otia, 180.— Adams, Shells of 

 Vt. 156 (1842).— DeKay, N. Y. Moll. 64 (1843).- Anonymous, Can. 

 Nat. II, 206, fig. (1857). 



Said to have been found from New England to the Saskatche- 

 wan, and in the District of Columbia. 



Fig. 222. 



Fig. 223. 



Planorbis 

 parvzis. 



Planorbis 

 parvus. 



Planorbis parvus, Say. — Shell horn-color or blackish; whirls 

 four, crossed by minute wrinkles ; concave above 

 and beneath, and equally exhibiting the volutions, 

 body generally subcarinate on the margin ; lip 

 rounded, and not vaulted above nor thickened ; 

 mouth within bluish-white. Breadth one-fifth of 

 an inch. 



Animal aquatic, brown, tentacula long, filiform, 



whitish, with a darker central line ; tail rounded. Probably 



the same species with that figured by Lister, tab. 139, fig. 45 ; pig. 224. 



it is very numerous in the Delaware, in company with the two 



preceding shells. (Say.) 



Planorbis parvus, Say, Nich. Ency. pi. i, f. 5 (1817, 1818, 

 1819) : Binney's ed. p. 45, pi. Ixix, f. 5. — Haldeman, Mon. 

 27, pi. iv, f. 19-23 (1844).— Go0LD, Invert. 209, f. 139 

 (1841).— Adams, Shells of Vt. 156 (1842).— DeKay, N. Y. 

 Molh 63, pi. iv, f. 58 (1843).— Anon. Can. Nat. II, 208, fig. (1857). 



Planorbis concavus, Anthony, Cat. of Shells of Cincinnati, no desc. 



Planorbis elevatus, Adams, Bost. Journ. Nat. Hist. Ill, 327, pi. iii, f. 16 

 (1S40).— Gould, Inv. of Mass. 207 (1841).— DeKay, N, Y. MoH. 65. 



Helix jyarvus, Eaton, Zool. Text-Book, 195 (1826). 



Said to inhabit the whole of eastern North America. 

 Mr. Say's type is still preserved in the Philadelphia Academy's 

 collection. 



