392 PROCEEDINGS OF THE ACADEMY OF [1899. 



4, the first red or corneous, somewhat projecting, the rest l)ut 

 slightly convex, more or less encrusted, but showing no cuticular 

 fringes, merely very fine spiral lines in well-preserved specimens: 

 the last whorl keeled throughout, somewhat impressed in the center 

 below. Aperture slightly oblique, semioval; peristome thin, 

 slightly expanded, with a small, moderately deep sinus above. 

 Umbilical callus thin. Operculum unknown. 



Alt. 5.5, diam. 6,8 mm. 



Alt. 4.3, diam. 6 mm. 



Diente, near Monterey, with S. frag ills. 



Distinct by its strong peripheral keel. Named in honor of Mr. 

 E. G. Vanatta, whose assistance in the identification of the pres- 

 ent collection is hereby acknowledged. 



Valvata humeralis, var. patzcuarensis n. v. 



This name is applied to the form from Lake Patzcuaro, noticed 

 in my paper on the shells of the Academy Exjiedition, these 

 Proceedings, 1891, p. 326. It is larger, far more robust and 

 elevated than V humeralis ; there is no angulation or shoulder 

 on the upper surface of the whorls; and the umbilicus is decidedly 

 smaller. V. drebeli C. and F., based upon V. humeralis Strebel, 

 differs in the less elevated and robust form, larger umbilicus, and 

 judging from Strebel's figures, the greater interruption of the cir- 

 cular aperture by the penultimate whorl. A specimen of var. 

 patzcuarensis measures: Alt. 5, diam. 5, length of aperture 2.5, 

 width 2.4 mm. 

 Polygyra rhoadsi n. sp. 



Shell depressed, with very low conic, almost flat spire, and small, 

 cylindrical umbilicus Avhich at the last whorl opens widely in an 

 arcuate rimation; last IJ whorls rib-striate, the ribs strong, nar- 

 row, separated by smooth intervals wider than themselves, continu- 

 ing on the base ; spire smoother, the first Ih whorls smooth. 

 Whorls slightly more than 5, moderately convex above, slowly 

 widening, the last whorl decidedly wider, very convex, having the 

 convex periphery situated above the middle of the whorl, con- 

 vexly slanting below the periphery, subangular at the margin of 

 the umbilicus, within which there is a groove parallel to the rima- 

 tion. Behind the lip the suture is abruptly and rather deeply 

 deflexed, and the whorl is deeply constricted. Aperture small. 



