576 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



VIVIPARID^E. 



Genus VIVIPARUS, Montfort. 



Syr.on. — Vivipare, Lamarck (1809), Phil. Zool. : aud (1812) Extr. d'un Cours (both times without exam- 

 ple, diagnosis, or figure). 



Viviparas, Montfort (1810), Syst., II, 247.— Gray (1847), Proceed. Zool. Soc, part XV, 155; and 

 (1,857) Guide to Syst. Distrib. Moll. Brit. Mus., I, 112.— Beck (1847), Amtl. Ber., 24, 

 Vers. Deutsch. Nat., 123.— Gill (1863), Proceed. Acad. Nat. Sci. Philad., 37.— Meek 

 (1865), PaliEont. Upper Missouri, 114. 



Henterum, Hiibn. (1810), Epist., 1. 



Paludina, Lamarck (1812), Extr. d'un Cours; and Hist. (1822), 172.— Deshayes (1830), Encyc. 

 M<5th., Ill, tab. ; and (1832) ib., 689.— Goldf. (1820), Naturg., 736.— Hartm. (1821), Sturms 

 Fauna, Abth. VI, Heft 5, 47.— Blainv. (1824), Diet. Sci. Nat, XXXII, 230; and (1825) 

 ib., XXXVII, 300; also (1825), Malac, 435.— Gray ( 1840), Turton's Man. (2d ed.),90 ; and 

 (1842), Synon. Moll. Brit. Mus., 90; also of numerous others. 



Vivipara, Sowerby (1813), Miu. Conch., I, 71. — Desor and Agassiz (1840), German transl. same, 

 54. — H. and A. Adams (1854), Genera Recent Moll., I, 38.— Binney (1865), Land- and 

 Fresh-water Shells N. Am., part III, 16. 



Eiym. — Viviparus, that brings forth Its young alive. 

 Type. — Helix vivipara, Linnaeus. 



Shell ovate or conoid-subovate, thin, usually with a small umbilical 

 perforation ; volutions rounded or more or less flattened ; surface smooth, or 

 with revolving lines or carinse ; epidermis olivaceous, often with revolving 

 bands of color ; aperture more or less regularly oval ; outer lip thin, straight 

 in outline, and continuous on a plane with the inner. 



Operculum corneous, entirely annular. 



Animal with lateral teeth of lingual ribbon oblong, arched, somewhat 

 pointed below, truncated and serrated above ; median tooth shorter, curved, 

 more or less rounded and serrated above, the middle denticle being larger 

 than the others. 



These mollusks inhabit rivers, lakes, and other bodies of fresh water, 

 and are widely distributed in the Northern Hemisphere. The genus is 

 related to Tulototna, Lioplax, and Campeloma. It may be distinguished, 

 however, from the latter two groups by its thinner shell, and by having its 

 outer lip straight in outline, and continuous on a plane with the inner, instead 

 of being sigmoid.* More important differences, however, although not avail- 

 able in palaeontology, are to be observed in the lingual teeth, which in Cam- 

 peloma and Lioplax have their upper margins smooth, or only very minutely 

 serrated, and the outer two on each side pointed and claw-shaped, instead of 

 truncated. Lioplax is also distinguished by having a subspiral opercular 



* Attention was first called to this well-marked character of tin- outline of the lip in this genus 

 by Professor Gill. 



