PLAXORBIS. 



115 



Fig. 191. 



Fig. 192. 



Form of PI. corjyulentus. 



Form of PI. corpulenttis. 



lentus. His original description and figure are given above. 

 Large globose forms of PL trivolvis are usu- 

 ally called Fl. corjjulentus in collections, and 

 have often been so labelled in the envois of 

 my correspondents. DeKay also describes 

 and figures a specimen of P. trivolvis as PI. 



corpulentus. Adams 



(Shells of Yt.) refers 



P. corpulentus to PI. 



trivolvis, and so Gould 



appears to decide in the Invert, of Mass. 



I have myself seen no specimens from the 



localities visited by Mr. Say while on Long's 



Expedition that are not forms of PL trivolvis. 

 The shells referred to PL corpulentus by Haldeman in his 

 Monograph, by Gould in the Exploring Expedition Mollusca, 

 and figured by Chenu (Z. c), and referred to in the following 

 museum register, are all from the West Coast. I believe them 

 to be distinct from PL corpulentus of Say, and that they should 

 receive another specific name. The description 

 of the animal given above is drawn from one of 

 this form. One of Haldeman's figures is copied 

 in my Fig. 192. It will be found to agree with 

 Fig. 191, drawn from one of the specimens in the 

 Smithsonian collection, No. 8119. A curiously 

 indented form from the West Coast is figured in 

 Fig. 193. 



P. corpulentus is catalogued from Guatemala by Mr. Tristam. 



Form of 

 PI. corpulentus. 



Planorltis trivol"«^s, Say. — Shell sinistral, pale jellow, brownish 

 or chestnut color, subcarinate above and beneath, particularly in the young 

 shell ; whirls three or four, striate across with fine, raised, equidistant, acute 



