﻿NEPITRONAIAS 285 



small one above it. and one lateral ; beak cavities shallow •• 

 muscle scars not deep, the anterior ones single ; nacre whitish 

 or grayish. 



Male shell long- rhomboid, the base line sliglitly curved or 

 straight, in old specimens a little incurved : lower posterior 

 ridg:e ending at the base lines. Female shell decidedly pro- 

 duced in the region of the marsupium, the posterior biangula- 

 tion elevated above the base line. 



Length (male) 43, height 24, diam. 15 mm. 



Length (female) 45, height 26.5, diam. 15 mm. 



Yzabel, Guatemala. 

 Unio vellicatns Reeve;, Conch. Icon., 1865, pi. xxii, fig. 103. 



Fischer and Crosse, Miss. Sci., II, 1894, p 610. 

 Nephronaias velHcatus Simpson, Syn., 1900, p. 597. 

 Uino raz'istellus von Marteins, Biol. Cent. Am., Moll., 1900, 



p. 516, pi. XXXVIII, fig. I. 



Reeve's figure represents a female shell, which differs a good 

 deal in form from that of the male. Von Martens believes 

 that this equals Morelet's Unio raznstellus, but Fischer and 

 Crosse claim that it does not. There are shells in the National 

 Museum, which came from Yzabel, Guatemala, that agree per- 

 fectly well with Reeve's figure and descri])tion, but are not 

 nearly as heavy nor so widely and distinctly biangulate behind 

 as are the figures given by von Martens. Sowerbv's figure of 

 raz'istellus in th.e Conchologia may be a young shell of that, 

 but T suspect that it is rellicata. 



Nephron AiAs mei.i.e.\ (Lea). 



Shell regularly elliptical, scarcely inflated, inequilateral, 

 rather solid, thicker in front, beaks prominent and minutely 

 undulated : surface sulcated throughout ; epidermis honey-yel- 

 low, bright, obsoletely rayed; posterior ridge rather full and 

 rounded, scarcely double in the specimen figured; pseudocar- 

 dinals rather large, erect, crenulate, two in each valve, laterals 

 nearly straight, elongated, double in each valve ; anterior cica- 

 trices impressed, posterior cicatrices confluent ; dorsal cica- 

 trices placed under the hinge plate behind the pseudocardinals ; 



