146 AMERICAN SPECIES OP VERTIGO. 



Angular, parietal and columellar lamellae are strongly de- 

 veloped, the parietal long, columellar crescentic, its inner end 

 curving downward. Palatal folds strong, the lower entering to 

 the dorsal side, its inner end curving downward. Type V. 

 milium. 



The peculiarities of Vertigo milium were first fully worked 

 out by Doctor Sterki, who considered it related to the Euro- 

 pean V. angustior (venetzii) ; but the relation seems to be one 

 of partial parallelism rather than of direct affinity. I may 

 mention that Dr. Sterki now considers the relationship 

 doubtful. 



The two species differ as follows : 



V. milwm. V. angustior. 



Dextral. Sinistral. 



Columellar lamella running Columellar fold spirally as- 

 downward inwardly. cending inwardly. 

 Lower palatal fold entering Upper palatal fold entering 

 deeply. deeply. 



Angustula has some features in common with the Cali- 

 fornian species of Sterkia, particularly the well-separated 

 angular and parietal lamellae and the descending inner end 

 of the columellar lamella; but there is probably no direct 

 relationship. 



Dr. 0. Boettger has considered V. ovatula, of the German 

 upper Oligocene and lower Miocene, to be closely related to 

 V. mitium. I have not seen that species, but as the form 

 of the columellar lamella as figured is entirely different in 

 V. ovatula and V. milium, the former evidently does not be- 

 long to Angustula. 



Two species are known: V. milium, no. 32, in which there 

 is a moderate swelling behind the outer lip, and V. bermu- 

 densis, no. 33, having a very high, massive crest. 



32. VERTIGO MILIUM (Old.). PL 13, figs. 1 to 7. 



' ' Shell minute, of a globosely-oval form, color a light chest- 

 nut; whorls four or somewhat more, obviously wrinkled 

 obliquely, rather convex ; apex bluntly rounded ; suture deep ; 



