THE NAUTILUS. 29 



Cannon Lake, Rice county, Minn., Types No. 22475, coll. 

 Walker. Cotypes in the collections of L. E. Daniels and the I'hila- 

 delphia Academy. Sixteen specimens of this fine large form were 

 collected by Mr. Daniels. They differ uniformly from the High 

 Island typical form in the particulars mentioned. 



Valvata lewisii Currier. PI. I, figs. 12 and 13. 



Dr. Lewis distinguished his V- striata by reason of its having the 

 " epidermis brown and very regularly striate." In the same paper 

 (Proc. P. A. N. S., 1856, 260) he describes " V. sincera" from the 

 same locality as having the " shell smooth and polished, white and 

 translucent." While unfortunately he does not seem to keep any 

 examples of his typical striata in his own collection, there is a set 

 from the Little Lakes labelled " sincera" which agrees with his de- 

 scription and which are the same as the form herein described as V. 

 bicarinata perdepressa. This leaves practically no doubt as to his 

 striata being the ordinary striate form. 



V. lewisii in its aggregate form is exceedingly variable in regard 

 to sculpture, ranging from the smooth or obsoletely striate var. heli- 

 coidea to a heavily ribbed form in which the ribs become low, closely 

 spaced lamella? very similar to the Isle Royale form of sincera 

 nylanderi. In well developed examples of this form, the ribs give a 

 brownish appearance to the shell, especially when not well cleaned, 

 and it is possible that such specimens were the types of Lewis' species, 

 and if varietal distinction were to be made between this and the more 

 common form in which the sculpture is " fine and close like the wind- 

 ing of thread on a spool," it should be considered as the typical 

 lewisii. l From the material before me, however, I fail to find suffi- 

 cient evidence of any racial distinction in this particular, (as there is 

 apparently in the case of V. sincera nylanderi) to justify such action. 

 The two forms apparently live together and grade indefinitely into 

 each other. 

 V. bicarinata Lea. PI. I, fig. 14. 



When I prepared my former paper on Valvata (Naut., XV, p. 123) 

 I had not seen Prof. B. Shimek's " Mollusca of Eastern Iowa," 

 (Bui. Lab. Nat. Hist. State Univ., la., I, p. 56, 1888) in which the 

 specific validity of this species is upheld. 



1 This will have to be determined from examination of authentic author's 

 specimens which I have not been able to obtain. 



