18 PROCEEDINGS OF THE ACADEMY OF [1896. 



branch of the V, base more tumid, and umbilicus of last whorl more 

 well-like. 



P. euglypta n. sp. PI. II, figs. 7, 8, 9. 



Shell obese, with low conic spire, rounded-angular periphery- 

 near the top of last whorl, sloping outer wall and convex, tumid 

 base. Umbilicated, a central perforation expanding at last whorl 

 to form an umbilicus about one-sixth the diam. of shell, and with 

 the wall rising almost vertically from its suture. Surface of outer 

 1^ whorls sculptured with sharp, strong and regular thread-like sig- 

 moid riblets, subobsolete and more numerous by intercalation in the 

 immediate vicinity of the umbilicus ; the inner whorls of spire 

 smooth. Whorls 4^-41, the inner slowly increasing, last whorl 

 much wider, very deeply constricted and excavated behind the outer 

 and basal lips. Suture impressed, deeply descending in front. 



Aperture extremely oblique, transversely oval, the lip forming 

 three-fourths of the circumference, upper and basal margins sub- 

 parallel. Outer lip broadly flaring, with a short lamella on its 

 inner edge, formed of a compressed, slightly entering portion joined 

 T-like to a short lamella parallel to the inner lip-edge ; basal lip 

 reflexed, bearing a compressed, entering tooth similar to the lower 

 portion of the T on outer lip. Parietal tooth like a narrow, slanting 

 V, the two branches united with the ends of the lip. 



Alt. 5*3. greater diam. 9"5, lesser 8'2 mill. 



Alt. 4"3, greater diam. 7"5, lesser 6'4 mill. 



Cinaloa (larger form) and Mazatlan (smaller form). 



A member of the P. ventrosula group, distinguished from veyitro- 

 sula, Hindsi, Richardsoni and bicruris by the very strong, sharp rib- 

 striation of the last IJ whorls. 



P. albicostulata n. sp. PI. II, figs. 4, 5, 6. 



Shell obese, with convex spire, periphery much above middle of 

 body-whorl, and tumid base. Umbilicated, the umbilicus narrow 

 and deep, with vertical walls, not much enlarging at last whorl, 

 where it measures about one-ninth the diameter of the shell; within 

 the umbilicus the last Avhorl has a deep spiral furrow, obliquely 

 passing into the groove behind the basal lip. Surface shining, the 

 latter two whorls sculptured with coarse whitish riblets with corneous 

 brown spaces ; inner whorls nearly smooth, corneous brown. Whorls 

 54, weakly convex, the last very obtusely angular at its origin, 

 becoming rounded and tumid on the latter half, deeply and narrowly 



