THE NAUTILUS. 



VOJ,. XV. MARCH, 1902. No. 11. 



A REVISION OF THE CARINATE VALVATAS OF THE UNITED STATES. 



BY BRYANT WALKER. 



Valvata tricarinata was originally described by Say in 1817 as 

 Cyclostoma tricarinata. It is one of the most abundant of the 

 smaller operculates of the Northern States and Canada, ranging from 

 the Atlantic coast westwardly at least as far as Manitoba and Iowa, 

 and south to Virginia and the Ohio river. It has three well-marked 

 varieties, which differ from the typical form only in the smaller 

 number or entire absence of the revolving carinae. 



In 1841 Dr. Isaac Lea described a Valvata from the Schuylkill 

 river, Pa., as V. bicarinata. 



Haldeman. in his "Monograph" (Ho) doubtfully refers Lea's 

 species to V. tricarinata as a bicarinate variety. W. G. Binney, in 

 1865 (L. & F. W. Shells III, p. 9), states that from an examination 

 of both Say's and Lea's types he is u convinced of the identity of the 

 two." Try on in his Continuation of Haldeman (1870) does not 

 mention the subject, and evidently acquiesced in Binney's decision. 



In this he has been followed by all subsequent writers ?o far as I 

 have been able to ascertain, with one exception. Mr. "W. A. Marsh 

 in his " Brief Notes on the Land and Fresh Water Shells of Mercer 

 Co., 111." (Conchologists' Exchange II, p. 80, 1887), separated the 

 two forms and recognized the validity of Lea's species.* 



From a careful examination of the material in my possession I am 



* The validity of V. bicarinata has been recognized by all recent Philadel- 

 phian conchologists. See NAUTILUS. VIII, p. 138. En. 



