WATSOisr: deficiencies in the veetiginin^. 



279 



The reproductive organs of Columella edentula in some respects 

 resemble those of the last species, while in other features they are 

 more like those of the genus Vertigo, though they differ from both in 

 the position of the receptaculum seminis. There can be no doubt, 

 however, that Hanna was right when he stated that this snail is far 

 more nearly related to Vertigo than to Punctum,^ a very different 

 genus, with a sigmurethrous excretory system and deep peripodial 

 grooves. Even in its jaw it seems to me that Columella edentula 

 more cloisely resembles Vertigo than Punctum, although the character 

 of this organ has formed one of the chief grounds for regarding this 

 animal as related to the latter genus. The multiple jaw of Punctum 



Trxincatellina 



Columella- 



Diagrammatic figures illustrating some of the differences in the reproductive 

 organs which appear to separate the type found in most of the British 

 species of Vertigo that possess male organs from the types occurring in 

 Truncatellina (when male organs are present) and in Columella. 



and Laoma is a very distinctive organ of peculiar structure, whereas 

 the jaw of Columella edentida seems only to differ from that of 

 Vertigo in that the oblong plates of which it is composed are less 

 closely united with one another. For in C. edentula the plates of the 

 jaw do not seem to be entirely disconnected, and in the genus Vertigo 

 the jaw often has the appearance of being built up of a number of 

 plates which are joined to one another but have not become entirely 

 fused together. The type of teeth found in the radula of Columella 



1 Proc. U.S. Nat. Mus., vol. xli, 1912, p. 371. 



