52 GASTROCOPTA, NORTH AMERICA, WEST INDIES. 



March, 1909, pi. 8, f. 7. STERKI, Nautilus, xxii, April, 1909, 

 p. 126. PILSBRY and FERRISS, Proc. A. N. S. Phila., 1910, p. 

 143, f. 366. 



This species, which replaces G. dalliana in western Ari- 

 zona, differs from that by the longer, more tapering shell, the 

 nearly or quite continuous peristome and the shape of the 

 columellar lamella, which has a vertical portion running down 

 from its inner end, longer than in G. d. media. The parietal 

 lamella runs forward further than in G. dalliana. In the type 

 locality it was found in company with G. hordeacella and C. 

 intuscostata, in the ratio of about 1 ~bilameUata to 16 hordea- 

 cella (text fig. 18). 



The specimens from Tempe are typical in all respects, and 

 occurred with the same and other species in the drift debris. 

 The largest and smallest measure : 



Length 2.35, diam. .83 mm. 



Length 1.95, diam. .8 mm. 



Subgenus PRIVATULA Sterki. 



Privatula STERKI, Nautilus, vi, p. 101, 1893, monotype P. 

 corticaria Say. 



The shell is whitish, without palatal callous or folds, the 

 columellar lamella minute, tubercular, angulo-parietal lamella 

 small and straight, its crest bilobed. 



The teeth are reduced more than in any other Gastrocopta. 

 Only one species is known. It is probably related to Albinula 

 and Sinalbinula, from which it differs by the absence of pala- 

 tal callous and plicae. 



15. GASTROCOPTA CORTICARIA (Say). PI. 10, figs. 1 to 4. 



The shell is minutely rimate, nearly cylindric, tapering 

 slightly to the very obtuse summit; thin, translucent- white, 

 almost smooth, very faintly marked with growth-lines. 

 Whorls 5%, quite convex, the last rounded basally, without a 

 crest behind the lip. Aperture irregularly oval; peristome 

 thin, well expanded, the lip-ends widely separated. Angular 

 and parietal lamellae united into one small bilobed lamellae, or 

 almost separate. Columellar lamella very low, subvertical, a 

 minute tubercle in front of its lower end. 



