The {Nautilus. 



Vol.. XXXI. JULY, 1917. No. 1 



A REVISION OF THE CLASSIFICATION OF THE NOETH AMERICAN 

 PATELLIFORM ANCYLIDAE, WITH DESCRIPTIONS OF 



NEW SPECIES. 



BY BRYANT AVALKER. 



The North American patelliform species of Ancylidae can be 

 conveniently and naturally arranged in eight genera and sub- 

 genera according to their shell characters. These can again be 

 grouped into three subfamilies characterized by the peculiarities 

 of the radula and jaw. 



It was hoped that a study of the soft .anatomy might reveal 

 other peculiarities co-ordinating with those of the radulae, and 

 lor that purpose with the kind assistance of correspondents in 

 England, South Africa and this countrj'' a very considerable 

 amount of alcoholic material, representing nearly all of the 

 characteristic groups, was collected, some of which will be very 

 dithcult to replace. This material was placed in the hands of 

 a distinguished zoologist, who undertook to work it up. After 

 appropriating and using the material thus obtained, it was a 

 matter of bitter disappointment, after having waited for three 

 years for the completion of the work, reported from time to 

 time to be in progress, to be informed by the gentleman that 

 he should not proceed further with the work as he did not think 

 that it would " pay for the trouble considering the more impor- 

 tant anatomical details that await study among other families 

 -of mollusks." 



Under these circumstances the subfamilies represented in (Uir 



