﻿274 Ni:i'IIR(>NAIAS 



I am very doublfiil wlicthcr this species occurs on the main- 

 land. Leas si>ecimens from Honduras, which bear that name, 

 are. I think, other species. I have seen specimens credited to 

 Cuba, which approach very closely to Ncphronaias tabascoen- 

 sis, but I am not certain that the locality is accurate. I append 

 the original description of Unio sccnnuatiis. 



"Testa ovata convexo depressa, longitudinaliter tenuissime 

 plicatula. castaneo-fulva. intus crerulescens ; umbones de])ressi, 

 striatim de corticali ; dens cardinals in valva dextra simplex, 

 triangularis, in utracjue comi)ressus. Alt. 30. Lat. 55. Diam. 

 17. Cacajajicara, in insula Cuba." 



Ni'TiiRONAis GUNDLACHi (Dunkcr). 



Shell elliptical or elliptic rhomboid, subsolid. subcompressed,, 

 somewhat inequilateral; most conspicuously inflated at or just 

 behind the middle, in front of this the outline is wedge-shaped 

 to near the front and where it rather suddenly narrows to the 

 anterior point ; posterior ridge scarcely developed, sometimes 

 feebly biangulate, and ending in a faint posterior biangulation ; 

 beaks low but sharp, their sculpture fine corrugated ridges, 

 which are doubly looped ; surface more or less sculptured with 

 concentric ridges, which are generally less developed in front 

 of the posterior ridge ; epidermis smoky-olive to green- 

 ish-yellow, generally with more or less distinctly developed 

 green rays ; left valve with two subcompressed pseudocardinals 

 and two delicate, nearly or quite straight, laterals ; right valve 

 with one subcompressed pseudocardinal, a vestigial one above, 

 and one lateral : muscle scars rather shallow ; dorsal scars 

 under the hinge plate and pseudocardinals. Nacre whitish, 

 distinctly and often strongly tinted with blue, .slightly iride- 

 scent behind. 



The male shells are often nearly evenly elliptical, and some- 

 times the length is only about one and a half times the width. 

 They are nearly straight, rarely somewhat curved below. The 

 female shell is wider behind than in front and has a wide, 

 rounded, often greatly developed marsuj^ial swelling. Its pos- 



