VALVATA. 287 



Valcata tricnrinala. Say, Journ. Ac;iil. ii. 17.'5; Bixxey's cd. 68. — Desiiayes, in Lam. 

 viii. 507; Tr. El. de Couch, pi. 72, figs. 4-6. — Mevke, Zcit. f. M;il. 1845, 121.— 

 IIaldejian, Mon. iii. pi. 1, figs. 1-4. — Gould, Inv. 22.5, fig. 156. — I)i-: Kay, N. 

 Y. Moll. 118, pi. 6, fig. 130. — Anonymous, Can. Nat. ii. 213, fig. — Adams, Thomp- 

 son's Vt. 152. — W. G. BiNXEY, L. and Fr. Shells, iii. 9, figs. 12-16 (1865). 



Vnlvalti carinata, Soweuby, Gen. Shells, xli. fig. 2. 



Valrnta unirannata, De Kay, N. Y. Moll. 118, pi. 6, fig. 129. 



Vidcat'i hi.arinata. Lea? Tr. Am. Phil. Soc. ix. 21 ; Obs. iv. 21 ; Proc. ii. 81, 83 ; Arch, 

 f. Nat. 1843, ii. 129. 



TropkUna carinata, Ciienu, Man. dc Conch, ii. 312, fig. 2232. 



Shell small, depressed, tliiii, transparent, and shining, of an em- 

 erald or liu'lit pea-u'reen color; whorls three or four, flattened 



"^^ Fiff. 549. 



at the summit, faintly marked by lines of growth, and sepa- 

 rated by a distinct suture ; each of the interior whorls has 

 one or two prominently raised, rounded, revolving lines or 

 keels, and the exterior one has three, one of which issues 

 from the lower junction of the lip and borders the umbilicus ; a 

 second originates from the upper junction of the lip, and circmn- 

 scribes the whorl ; the third midway between this and the 

 suture, thus giving the whorls a prismatic or quadrangular 

 instead of a cylindrical appearance ; aperture circular, mod- 

 ified by the keels ; lip simple, surrounding the aperture, 

 except a small space between the two lower keels ; umbil- ofT^'va^ 

 icus broad, deep, funnel-shaped. Height, one tenth of an Eukr-ed. 

 inch ; breadth, seven fortietlis of an inch. 



Yar. simplex, without the keels. Professors Benedict and Adams 

 have found this species in Vermont ; and in very many instances it 

 is perfectly simple and cylindrical, individuals occurring with every 

 degree of carination, showing that it is still the same species. In 

 this State, the large, funnel-shaped umbilicus is the best charac- 

 teristic. 



It is found in most of our small lakes, usually under stones, or 

 sheltered by the deserted shells of some of the fresh-water mussels. 

 It has also been found from Pennsylvania to Council Bluff and 

 Methy Lake (lat. 57^). 



The shell is usually rendered somewhat opaque by an earthy coat- 

 ing, which seems to answer the purpose of an epidermis ; but, when 

 this is removed, the surface is shining and pearly, of an emerald- 

 green color, lighter on the keels. It is one of our most curious 

 shells. 



