POLYGYRELLA. 79 



triangular or crescentic, the lip not in the least expanded, blunt, 

 thickened within the edge by a white rim, simple or two-toothed ; 

 parietal wall smooth or with an erect tooth. Type P. polygyrella, 

 pi. 31, figs. 28, 29, 30. 



External anatomy unknown. Genital system (in P. polygyrella, 

 the only species yet investigated) without accessory organs, like that 

 ofPolygyra (pi. 31, fig. 31). 



Jaw low and wide, with no median projection, having numerous 

 strong vertical ribs, denticulating its margins (pi. 31, fig. 32). 



Central teeth tricuspid, laterals bicuspid, marginal teeth bicuspid, 

 the ectocone simple or bluntly bifid (pi. 31, fig. 41). 



Distribution : California, Washington, Idaho and Montana. 



The anatomy of the species of this genus is, as far as it is known, 

 the same as in Polygyra except that the jaw is wider with more ribs. 

 The shell differs from Polygyra in its absolutely unexpended blunt 

 lip and its glassy texture. It may be distinguished from the Palse- 

 arctic genus Gonostoma by the characters of the shell just mentioned 

 (Gonostoma having an opaque shell with expanded or reflexed lip), 

 and by the simplicity of the generative system. The relationship of 

 Polygyrella to Polygyratia cannot be decided until the anatomy of 

 the South American genus is made known. 



[Note. Mr. Binney's classified Synopsis of North American land 

 shells, in which the name Polygyrella first appeared, is referred to 

 as " a mere proof" by Professor Joseph Henry, Secretary of the 

 Smithsonian Institution, who adds that it " should not be quoted as 

 authority or referred to as a published work." This suggestion 

 cannot be followed. The Synopsis is not in any ordinary sense a 

 proof-sheet. A. large edition of it was printed and widely circulated, 

 as an official publication of the Smithsonian Institution.] 



Subgenus POLYGYRELLA Binney, 1863. 



Polygyrella BINNEY, Smithsonian Miscellaneous Collections, no. 

 000, p. 5, Dec. 9, 1863 (no description; type H. polygyrella). 

 Polygyrella Bland, BINNEY & BLD., in Land and Fresh-Water 

 Shells of North America, p. 112, type H. polygyrella Bid. & Coop. 

 W. G. BINNEY, Terr. Moll, v, p. 289 (jaw and dentition), and 

 Second Supplement to the same, p. 36 (genitalia). PILSBRY, Proc. 



