﻿266 NlirilRONAlAS 



iigurcs. that 1 can have but little doubt that tiiey are his 

 s[)ecies. 'I'liev are :i trille narrower behind than the ty[)(' and 

 the epidermis is daiicer in the vicinity of the beaks. The 

 shell is occasionally faintly rayed. 

 Nf.phuon.mas Fi.ucki r>artsch. 



"Shell elliptical, moderately inflated, attenuated posterio- 

 ventrally ; slo[)ing' <j;^ently and evenly dorsally from a line ex- 

 tending from the umbones to the posterior ventral angle. 

 Dorsal line evenly arcuate, curving a little more abruptly an- 

 teriorly than at the posterior end ; ventral margin almost 

 straight or slightly concave. In some, [)resumably the females, 

 the shell is somewhat drawn out ventrally at the posterior 

 margin, and in such the ventral outline necessarily appears 

 more concave. Surface marked by numerous very strong, 

 concentric lines of growth and crinkly, radiating rays, which 

 are more pronounced on the anterior end, gradually fade out 

 from the middle of the shell posteriorly. Periostracum shin- 

 ing, dark brown at the umbones, fading gradually to greenish- 

 yellow at the edge. Umbonal cavity moderately deep. Pseu- 

 docardinal of the right valve strong, triangular, deeply notch- 

 ed, (almost bifid, by the deep, vertical A-shaped notch in old 

 specimens), with numerous, fine, secondary notchings. Pseu- 

 docardinals of the right valve rather slender, finely notched, 

 inclosing a A-shaped cusp between them, which corre- 

 sponds to the A-shaped notch in the other valve. Laterals 

 narrow, slightly arcuate and obliquely ridged. Dorsal mus- 

 cle scars feeble. Nacre bluish-white at the margin, shading 

 to livid-olive dorsally. 



Length 64, height 26.7, diani 17.6 mm." ( liartsch). 



Tvpe locality, Wounta River, northwest of Kukallaya, Nic- 

 aragua. 

 Nephronaias flucki Uartsch, Pr. U. S. Nat. Mus., 1906, 



XXX. p. 393, pi. xxvir, figs. 2, 3; xxviir, figs. 2, 3: xxix, 



figs. T, 3. 



