HOLOSPIRA. 91 



tapering to about 0.7 mm. within the penultimate whorl. 

 The cylindrical portion of the shell passes very gradually 

 into the slowly tapering cone (pi. 23, fig. 74). 



15. H. SEMISCULPTA Stearns. PI. 16, figs. 3, 4. 



Shell dextral, elongately cylindrical, pupiform, largest in 

 the middle, tapering above and below, with fourteen to fifteen 

 whorls; whorls somewhat convex; sutures distinct, though 

 but slightly impressed. The upper two or two and a half 

 whorls which form the apex are smooth, slightly tortuous, 

 papillose. The succeeding four to five whorls are finely ob- 

 liquely plicated; the middle whorls, four to five in number, 

 are nearly or quite smooth, the sculpture when apparent being 

 inconspicuous. The lower three or three and a half whorls 

 are marked by sharp, thin, and rather obliquely curved 

 lirae, which increase in number or closeness as the mouth is 

 approached. The termination of the basal whorl projects 

 considerably, is sharply angulated above on the projecting 

 portion, which is also obtusely angulated on the under side. 

 Aperture continuous, moderately effuse, roundly ovate, and 

 flatly rimmed. Umbilicus a simple chink. Shell of a deli- 

 cate pinkish-white, with a tint of faint purple on some of the 

 upper whorls. Length 22-23y 2 , diam. 5y 2 -6 mm. (Stearns.) 



State of Chihuahua, Mexico, in a canon above San Carlos, 

 on limestone cliffs (T. W. Stanton) ; three specimens, no. 

 102310, U. S. Nat. Mus. 



Holospira semisculpta STEARNS, Proc. U. S. Nat, Mus., xiii, 

 1890, p. 208, pi. 15, f. 1, 4. 



Closely allied to H. coahuilensis W. G. B. and H. pasonis 

 Ball, but smaller than either, with more whorls. Dall ascer- 

 tained the internal pillar to be simple and smooth. 



16. II. COAHUILENSIS (W. G. Binney). PL 23, figs. 66-69. 



Shell rimate, cylindrically ventricose, thin, smooth or deli- 

 cately striate on the upper whorls, strongly ribbed on the last 

 two; white; composed of 12 ventricose or flattened whorls; 

 apex obtuse, shining ; upper 3 whorls of about equal diameter 

 and smooth, the next 4 rapidly increasing in width and stri- 



