﻿3i6 ri.AC.ioi.A 



is great!}- ihickcncd. the surface is badly eroded, so that the 

 rough, black epidermis remains only around the later growth, 

 and it has a decided marsupial swelling, thus precluding the 

 l)ossibility that the species can be a Qiiodnila. 



(irou]) of f'l(ii!;i()!a iiicanii!;iicvsis. 



Shell nuich like that of cyroioidcs, but simply covered with 

 coarse, irregular, concentric ridges, and having no radiating 

 grooves or wrinkles, faintly ra\ed in unbonal region. Animal 

 as in the cyrcnoidcs grouj). 



Pi.AGioi.A xiCAKAC.riCNsis (i.ea). 



Shell suboval. rather inflated, subsolid. rounded below and 

 obliquely truncated above in front, with a \\ell-developed,. 

 slightly rounded posterior ridge ; l)eaks somewhat full and 

 high, their sculptiu-e consisting of a few fine corrugations, 

 which are somewhat doubl}- looped ; surface strongly concen- 

 trically sulcate. covered with a yellowish-green or olive-green 

 epidermis, which sometimes shows a few faint rays ; left valve 

 with two suibcompressed pseudocardinals and two laterals, the 

 upper lateral small ; right valve with two pseudocardinals, the 

 upper compressed and small, and one lateral, sometimes with 

 a vestige of a second lateral below it ; beak cavities moderate, 

 not compressed ; anterior scars impressed ; posterior scars 

 shallow ; nacre bluish-white, sometimes tinted yellowish or 

 flesh-colored in the cavities of the shell. 



Male shell with rounded base-line, pointed behind at some 

 distance above the base: female shell gencrallv higher than 

 the male, with a wide, roimded marsupial swelling, the lilunt 

 posterior point much elevated. 



Length (male) 46. height 32. diam. 23 mm. 



Length (female) 40. height 30. diam. t8 mm. 



Nicaragua. 

 Unio nicaraguensis Lka. Pr. ;\c. N. Sci. Phila.. XTT. t868. p. 



95: Jl. Ac. N. Sci. Phila.. A'T. 1868, p. 206. pi. xr.in. fig. 107: 



Obs.. XTT, t86o, p. 5^\ pi. xi.in. fig. 107. 

 Margaroii (Unio) nicaraf^u^nsis T^ka, Syn.. 1870. p. t^^. 

 Phiisiola nicayas^iirnsis Stmpsox, Syn.. tf)0o, p. 607. 



