112 



LAND AND FRESH- WATER SHELLS OF N. A. [PART IE 



Cat. No. No. of Sp. Locality. j From whom received. | Remarks. 



9122 I 1 



Dr. Gould. 



Subgenus HELISOMA, Swains. 



Shell ventricose, the spire sunk below the body whirl ; whirls 

 few, often aiigulated. 



Fig. 187. 



I'laiiorliis ainiaioii, Gould. — Shell large, discoid, subconic, deli- 

 cately striate ; left side broadly and deeply concave, showing four obtusely 

 carinated whirls ; right side concave, showing 

 two and a half rounded whirls ; aperture ovate- 

 triangular, sometimes quite expanded on each 

 side ; axis | to 1, diam. 5^ to | inch. 



Found by Dr. T. H. Webb, in the Cienaga Grande, 

 or Colorado Low Desert, and also by Mr. W. P. 

 Blake. 



The specimens differ greatly in size, and in the 

 development of the aperture ; but all agree in the 

 peculiar slope of the outer volution, giving them 

 a conical or dome-shaped form when lying on the 

 left side. Fully developed specimens are much 

 like P. corpulentus, Say, but the shape of the volu- 

 tion and aperture difier, and the striae are less 

 coarse, and more like P. yhihratus, Say. ( Gould.') 



Planorhis ammon, Gould, Proc. Bost. Soc. Nat. 



Hist. V, 129 (1855) ; Otia, 216 ; Pac. R. R. 



Rep. V, 331, pi. xi, f. 12-18 (1857) ; Prel. 



Rep. 23 (1855). 

 Planorhis trnskii, Lea, Pr. Phil. Acad. Nat. Sc. 



1856, VIII, bO. 



Planorhis an/mon. 



It is also said to have been found in 

 lagoons, Sacramento Yalley, and Ocogo 

 Creek, California. Fig. 187 is copied from those of Gould. 



No. 9169 of the collection was labelled "P. tratikii," by Dr. 

 Trask. It appears to be identical with Gould's shell. Fig. 188 

 is drawn from Mr. Lea's original specimen of I\ traakii, and his 

 description is given below. 



