310 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 85 



the base fewer and much more distantly placed than those of G. (P.) 

 assimilis guirensis^ which it most nearly resembles. 



The type, U.S.N.M. no. 4G8745, is a complete specimen, having 

 6.4 whorls and measuring: Length 1G.3 mm; greater diameter, 11.8 

 mm ; lesser diameter, 8.2 mm. 



CHONDROTHYRELLA (PLICATHYRELLA) ASSIMILIS CISNEROSI, new subspecies 



Plate 25, Figure 6 



This, the largest race of G. (P.) asshnilis, was collected by Cisneros 

 in the Sierra Rosario. It is dark horn-color, and the broken tip shows 

 the dark columella. It is roticulately latticed but only fe«bly cusped 

 at the intervals of the axial riblets and spiral threads. Within the 

 umbilicus the spiral threads are very strong and rendered conspicu- 

 ously cusped by the axial threads. 



The type, U.S.N.M. no. 367882, has 3.9 whorls remaining and 

 measures : Length, 15.3 mm ; greater diameter, 12.8 mm ; lesser diam- 

 eter, 9.1 mm. 



CHONDROTHYRELLA (PLICATHYRELLA) ASSIMILIS GUIRENSIS, new subspecies 



Plate 25, Fiouke 4 



This race was collected by Arango in the Sierra la Guira northwest 

 of San Diego de los Banos. It has the axial riblets on the early post- 

 nuclear whorls very distantly spaced, while those of the last whorl 

 are but slightly elevated and separated by spaces as wide as, or only 

 a little wider than, the ribs. In this subspecies the spiral threads on 

 the anterior part of the base are less strong, more numerous, and 

 closer spaced than in G. (P.) assimilis assimilis, with which it shares 

 a faintly yellow peristome. 



The type, U.S.N.M. no. 367886, has 4.7 whorls remaining and 

 measures : Length, 14.0 mm ; greater diameter, 11.0 mm ; lesser diam- 

 eter, 7.6 mm. 



CHONDROTHYRELLA (PLICATHYRELLA) ASSIMILIS GEMMA, new subspecies 



Plate 25, Figure 3 



This, the smallest of all the races of this species, comes from Mogote 

 Colorado, one of the limestone blocks on the east side of the Rio San 

 Diego, a short distance north of San Diego de los Banos. Its minute 

 size, combined with the closely spaced axial riblets on the early post- 

 nuclear whorls, readily distinguishes it from the other subspecies. 



The type, U.S.N.M. no. 468747, has 5.8 whorls remaining and 

 measures: Length, 11.4 mm; greater diameter, 7.7 mm; lesser diam- 

 eter, 5.9 mm. 



