﻿282 NIvrHRONAlAS 



dorsal scars ; muscle scars well impressed, the anterior ones 

 rough ; nacre rich coppery-purple, slightly iridescent behind ; 

 pallial line crossed by faint, radiating- ridges. 



Male shell decidedly long rhomboid, with a straight base 

 line, the lower ])osterior ridge ending at this line. Female 

 shell slightl\- obovate, subrhomboid ; the base line rounded and 

 somewhat produced behind the middle ; lower posterior ridge 

 ending above the base. 



Length (male) 58, height 35, diam. 19 mm. 



Tabasco. Mexico ; small stream near I'unta Gorda, Belize, 

 Honduras. 

 Unio tal^jscocnsis Charpentiicu in Ki;stf,k, Conch. Cab. Unio. 



1856. p. 1 53' pl- xLiv, fig. 3. 

 Margarun (Unio) tabascoensis Lea. Syn., 1870, p. 61. 

 Nephronaias tabascoensis Simpson, Syn., 1900, p. 596. 

 Unio cuprinits tabascoensis von Martens. 15iol. Cent. Am., 



Moll., 1900, p. 505. 



The shell figured in Kuster is a male and is straight on the 

 base line and has a considerably developed jiosterior point. Its 

 outline is almost exactly that of the Unio persnlcatus Lea, and 

 it differs from that si>ecies only in having a silvery instead of 

 a purple nacre and in being uniform colored, while persulcata 

 has a yellow band reaching from the beaks to the posterior 

 region. 



Xf.piironaias pi.icatula ( Charpenticr in Kuster). 



Shell elongately obovate. inequilateral, somewhat convex, 

 densely concentrically ridged; beaks longitudinally undulately 

 plicate, rather prominent; epidermis fuscous-olive; pseudocar- 

 dinals bipartite, solid ; laterals rather remote, moderate ; nacre 

 beautiful violet, shining. 



Mexico, Punta Gorda, Belize; Honduras. 

 Unio plicatulns Charprntikr in Kustkr, Conch. Cab. Unio, 



1856, p. 154, pi. xuv, fig. 4- 

 Nephronaiias plicatidns Simp.son. Syn.. 1900. p. 597. 



The figure in Kuster no doubt represents a female shell, as 

 the base line is rather strongly curved, especially in the region 



