542 



PROCEEDINGS OF THE ACADEMY OF 



[Nov., 



umbilicus (contained about 4^ times in the diameter of shell), which is 

 well-like and enlarges very little at the last whorl, where but a very narrow 

 area of the preceding whorl is exposed. Surface glossy, marked with 

 growth-wrinkla*, more distinctly striate behind the lip; pale brown. 

 Whorls 4f to 5, convex, the last subangular in front of the aperture, 

 soon becoming rounded, with the periphery well above the middle; 

 it is deeply contracted behind the outer and basal lips, and descends 

 abruptly in front ; within the umbilicus it is flattened but not furrowed. 

 The aperture is transversely oblong. Parietal tooth Y-shaped both 

 branches curved, the outer one slender and nearly but not quite 

 reaching the upper termination of the lip; lower branch stronger, 

 nearly reaching the termination of the columellar lip. Within the outer 

 lip there is a compressed tubercle with a callous buttress or concave 

 plate above it. In the basal margin there is a similar compressed 

 tubercle, with a weak callus (scarcely a tooth) between it and the 

 columella. 



Alt. 4.2, diam. 8.8, width of umbilicus 2 mm. 

 " 4, " 8 mm. 



Guadalajara, State of Jalisco. Types No. 99,513 A. X. S. P. 



Polygyra guadalajarensis n. sp. 



This species is related to P. ventrosula hindsi (Pfi\), from which it 

 differs chiefly by the much larger cavity of the umbilicus, which 

 enlarges at the last whorl less than in any of the related species known 

 to me. 



The two species described above belong to the group of P. ventrosula, 

 — the most difficult group of Mexican Polygyras. 



This group includes shells in which the parietal tooth is distinctly 

 V-shaped, and the outer lip has a well-developed concave plate or but- 



