PLANORBIS. 



125 



Flaiiorllis ailtrosus, Coxkad. — Shell dextral, not depressed; 

 whirls three ; spire profoundly indented or concave, with the summit of 

 the body whirl angular ; inner volutions angulated, umbilicus profound, 

 with the margin and inner volutions angulated ; body whirl abruptly 

 dilated near the aperture ; aperture longitudinally subovate, dilated. 



Raudon's Creek, near Claiborne, Alabama, adhering to limestone rocks. 

 {Conrad.) 



Planorhis anirosits, Conrad, Am. Journ. Sc. [i], XXV, No. 2, p. 343 (1834). 

 — DeKay, N. Y. Moll. 66 (1843).— Mullek, Syn. Test. 1834 prom. p. 

 34 (183tJ). 



T have seen no authentic specimen of this shell. 



ScBGEXus MENETUS, H. & A. Ad. 

 Shell depressed ; whirls rapidly increasing, ])cnphery angulated. 



Moquin-Tandon uses Hippeidis of Agassiz instead of Menetus 

 as a name for this section. I do not have access to the descrip- 

 tion of Hippeutis, and therefore follow H. & A. Adams in using 

 Menetus. 



Fig. 208. 



PIanor"bis opercularis, Gould. — Shell small, dextral, much de- 

 pressed, lenticular, with a prominent blunted keel at the periphery defined 

 by a marginal, compressed line ; tip sunken ; beneath umbilicated for 

 about one-third the breadth of the base, showing three 

 volutions, convex, surface rather rude and indented, 

 marked with irregular, coarse, much arcuated lines of 

 growth, and here and there a few obscure, raised, re- 

 volving lines ; color dark chestnut-brown, a little cloud- 

 ed ; whirls above four, slightly convex ; suture well de- 

 fined, impressed ; aperture transversely sub-rhombic, 

 lip above slightly declining, at periphery acute-angled, 

 beneath arched, lips embracing three-fourths of that 

 part of the whirl which is beneath the carina. Length 

 one-fourth, diam. one-sixteenth inch. 



Sacramento River, California. 



Allied to PL exacutus, but is larger, less compressed 

 and less delicate, and the periphery instead of being 

 sharp-edged, has a blunted keel like PL carinatus. 

 (Gould.) 



C(®) 



V- 1 



Planorhis 

 opercular is. 



Planorhis opercularis. Gould, Proc. Bost. Soc. Nat. Hist. II,. 212 (1847) 

 U. S. Ex. Ex. Moll. 113, f. 132, 132 a, 132 h (1852) ; Otia, 42. 



