THE NAUTILUS. 



VOL. XX. JULY, 19O6. No. 3. 



NOTES ON VALVATA. 



BY BRYANT WALKER. 



In 1824 Say described an ecarinate form of Valvata from the 

 "Northwest Territory "as V. sincera. In 1856 Dr. James Lewis 

 described a somewhat similar shell from the Little Lakes, N. Y., as 

 V. striata. W. G. Binney (L. & F. W. Shells III, 13.) in 1865, 

 had "no doubt of its identity with V. sincera." In this decision 

 Dr. Lewis seems to have acquiesced as it is not mentioned at all in 

 his " L. & F. W. Shells of New York " (1874), nor was it listed in 

 his collection. 



In 1868, however, A. 0. Currier (Shell-bearing Moll, of Mich. p. 

 9.) declared Lewis' species to be a valid one and striata being pre- 

 occupied proposed for it the name of lewisii. 



Binney's opinion seems to have generally prevailed among Amer- 

 ican conchologists until within the last year, when Dr. W. H. 

 Dall (Alaska XIII, pp. 22 & 23) declared them to be specifically 

 distinct. 



From a critical study of several hundred specimens from more 

 than fifty different localities, I have come to a similar conclusion, 

 viz : that there are two distinct species which have hitherto passed 

 as Say's sincera. The one, smaller, more elevated, with a smaller 

 umbilicus, the other, larger, more depressed and widely umbilicated. 

 Both vary in sculpture from being nearly smooth, with subobsolete 

 strias to very strongly sculptured forms in which the striae are ele- 

 vated in " thin, sharp lamellae. " 



Owing to the prevalent confusion of the two forms, the existing 



