GASTROCOPTA, NORTH AMERICA, WEST INDIES. 27 



peristome is thin, slightly expanded, strengthened a short 

 distance within wth a low callous rib. The parietal lamella 

 appears distorted and angular in front view ; seen from the 

 base it is seen to consist of an angular and a parietal lamella, 

 completely united inwardly. The columellar lamella is thick 

 and slants upward from within. The basal fold is strong, 

 arising on the callous but extending inward beyond it. The 

 lower palatal fold is large and pliciform, more or less im- 

 mersed, standing chiefly inward from the palatal callous. 

 The upper palatal fold is much smaller, and stands rather 

 near the lower, upon the palatal callous. There is a small or 

 minute suprapalatal fold, also on the callous. 



Length 1.75, diam. 1 mm. 



Trinidad, Colorado, type no. 93052, A. N. S. P. (figs. 9, 10; 

 pi. 2, fig. 7). Also Silver Lake, Kansas (fig. 11). 



This race differs from G. holzingeri by its more slender, 

 cylindric shape and the form of the columellar lamella, which 

 ascends straightly and runs forward (pi. 2, fig. 7), while in 

 holzingeri it ascends further and has an arched shape. 



Subgenus VERTIGOPSIS 'Cockerell' Sterki. 



Vertigopsis Ckll. MS, STERKI, Nautilus, vi, 1892, p. 4; p. 

 101, 1893, type P. curvidens Old. 



Vertigopsis differs from Sinalbinula chiefly by the weak- 

 ness of the parietal lamellee, the angular being very small or 

 wanting, and the parietal short and simple. 



It is not directly related to other American groups of the 

 genus, having evidently been derived from the Asiatic section 

 Sinalbinula. 



The species are illustrated on plates 3, 4 and 5. 



Key to Species. 



a. With a distinct palatal callous. 



&. Shell ovate-conic, usually with 7 teeth; length 1.7 

 to 2 mm. G. tappaniana, no. 5. 



6 1 . Shell oblong-conic or cylindric. 



c. Oblong-conic, with 5 to 8 teeth ; 1.5 to 1.8 



mm. long. G. pentodon, no. 4. 



c 1 . Cylindric, with 5 teeth. G. p. gracilis, no. 4a. 



