﻿26o Ni;i'lIU()\,\l AS 



This may be a young- ai'cryi and it has about the same out- 

 lines as that species has at a corresponding size. It is a very 

 much thinner shell and is differently colored within and with- 

 out. It shows traces of faint, bluish-green rays at the posterior 

 end. 



Group of Nephroiiaias macnielii. 



Shell solid, slightly sulcate, biangulate behind, covered with 

 a dull, olivaceous epidermis and having faint, bluish-green 

 rays ; beaks rather full, sculpture feeble, consisting of slightly 

 outlined ridges, which are somewhat doubly looped, the looped 

 lines becoming swollen or nodulous at their bases ; pseudocar- 

 dinals compressed and ragged ; laterals obliquely striated ; 

 nacre bluish-white, very soft and brilliant, somewhat irides- 

 cent posteriorly ; male and female shells ditifering but slightly. 

 Animal unknown. 



Nkphronaias macnieui (Lea). 



Shell irregularly long elliptical, scarcely subsolid, subcom- 

 pressed, with a well-developed, double posterior ridge, which 

 ends in a more or less distinctly marked biangulation ; beaks 

 moderately elevated but not inllated, turned forward over 

 a small lunule ; tiieir sculpture consisting of rather fine, double 

 loops, the loojis being but slightly connected together ; anterior 

 a little narrowed and rounded ; surface irregularly, concentri- 

 cally striated, brownish or tawny green, sometimes having a 

 few faint, green rays ; left valve with two radical pseudocardi- 

 nals and two laterals ; right valve with one pseudocardinal 

 sometimes slightly split into denticles and one lateral ; anterior 

 cicatrices impressed ; nacre bluish. 



The male shell is nearly or quite straight on the base, while 

 that of the female is slightly produced in the post-basal region. 



Length 60, height 35, diam. t8 mm. 



Nicaragua. 

 Unio macnicln Lea, Pr. .\c. N. Sci. TMiila., XIIL 1869. p. 124; 



Jl. Ac. Nat. Sci. Phila., 1874, p. 25. pi. viii, fig. 22; Obs., 



Xin, 1874, p. 29, pi. VIII, fig. 22. 

 Nephronaias macmeUi Simpson, Syn., 1900, p. 593. 



