lOG 



LAND AND FRESII-WATER SHELLS OF N. A. [PART II. 



Plaiiorbis glaliratus, Sat.— Shell sinistral ; whirls aboiit five ; 

 glabrous or obsoletely rugose, polished, destitute of any appearance of 

 carina; spire perfectly regular, a little concave; umbilicus large, regu- 

 larly and deeply concave, exhibiting all the volutions 

 to the summit; aperture declining, remarkably oblique 

 with respect to the transverse diameter. Breadth 

 nearly nine-tenths of an inch. 



Inhabits South Carolina. Cabinet of the Academy. 

 Presented to the Academy by Mr. L'Hermenier, of 

 Charleston, an intelligent and zealous naturalist. He 

 assured me that this species inhabits near Charleston. 

 It somewhat resembles large specimens of the P. iri- 

 volvis, of the American edition of Nicholson's Eiicj'c, 

 but differs in the total absence of carina, and in having 

 a more smooth and polished surface, as well as a de- 

 clining and more oblique aperture, and a more profound and much more 

 regularly concave umbilicus. (^Suy.) 



Planorbis glahratus, Say, Jour. Acad. Nat. Sc. I, 280 (1818) ; Nich. Enc. 

 3d ed. (1810) : Binxey's ed. p. 51, 61. — Haldeman, Mon. 11, pi. ii, 

 f. 1-3 (1844).— DeKay, N. Y. Moll. QQ (1843). 



It is said to be found in Mexico, Louisiana, and Oregon, wliicb, 

 with Say's locality, gives a wide range to this species. 



My figure of PI. glahratus is drawn from a specimen corres- 

 ponding with that figured by Haldeman, and generally acknow- 

 ledged to be this species. 



Planorbis glabrattis. 



Fig. 180. 



P. tumene. 



PlaitiorlJis tumeiis, Carpextek. — Shell rapidly 

 swelling, small, horn or reddish smoke-colored ; whirls four 

 or five, with light waving strias ; sutures deeply impressed ; 

 on one side subangulate or subcarinate near the suture, on 

 the other rounded ; umbilicus very deep ; aperture with a 

 sinuous edge, one side standing out above, flattened below, 

 the other flattened above, produced below, capacious and 

 rounded ; labium very thin. 



This species is so variable that it is difficult to describe it 

 soU^ to include all the specimens and yet separate it from 

 its congeners. Aberrant individuals on the one side closely 

 approach P. ajftnis, on the other P. lentus, Say. The three 

 may hereafter be proved identical ; but the general habit of 

 P. tumens, as gathered from repeated examinations of many 

 hundred specimens, is sufficiently distinct from the Jamaica 



