GASTROCOPTA, NORTH AMERICA, WEST INDIES. 41 



microscopically rugulose ; aperture of moderate size, rounded 

 below, truncated above, with a sinus occupying the upper 

 half of the palatal side. Lamellas and folds: angulo-parietal 

 large ; angular at its inner end joining the side of the parietal, 

 Avith a curve reaching the margin at the supero-parietal 

 angle; parietal very high, strongly curved, the (inner) con- 

 vexity toward the columella, its front end at a rather large 

 distance from the supero-columellar angle ; columellar spiral, 

 with its front end on the parietal wall, its inner part not 

 visible ; basal radial, lamellar, high ; inferior palatal fold very 

 deep in the throat, long, lamellar, curved downward over the 

 basal, visible only from the outside; superior palatal fold 

 quite short, high, tooth-like, in front of the inferior. Alt. 2.3, 

 diain. of spire 1.1, whole diam. 1.5 mm. ; apert. alt. 0.8, diam. 

 0.6mm." (Sterki). 



Arizona: Nogales (type locality; Ashmun) ; debris of Santa 

 Cruz River, at Amado's ranch, above Tucson; Salt River 

 debris, Tempe; debris of San Pedro River at Benson; Dra- 

 goon Mountains at several stations; Chiricahua Mountains in 

 White Tail canyon and below Paradise (Pilsbry and Ferriss). 

 Never at high elevations. 



Bifidaria perversa STERKI, Nautilus, xii, Dec. 1898, p. 90. 

 PILSBRY and FERRISS, Proc. A. N. S. Phila., 1906, p. 144; 

 1910, p. 137, fig. 29. ASHMUN, Nautilus, xiii, p. 14 (Ephraim 

 canyon, Santa Rita Mts.). 



This species resembles G. ashmuni rather closely. The 

 straightened part of the last whorl is somewhat longer, though 

 the length of the free portion varies. There are also slight 

 differences in the details of the teeth. Fresh specimens are 

 very pale brown. As in G. ashmuni, the shell is extremely 

 thin. It has been found only in Maricopa, Pima, Santa Cruz 

 and Cochise counties, in southern Arizona. I have never 

 found it so abundant as G. ashmuni. 



9. GASTROCOPTA ASHMUNI (Sterki). PL 6, figs. 5, 6, 7. 



Shell cylindro-conical, with the apex rather acute, base 

 perforated-rimate ; whorls five, convex, with a rather deep 

 suture, regularly increasing, the last somewhat protracted, 



