﻿UNITED STATES AND NORTHERN MEXICO. 357 



distance) a direction nearly parallel with the ligament. The epidermis in most of the 

 specimens before me is of an olive brown on the first stage of growth, and afterwards 

 quite yellow. In some specimens, however, it is dark brown all over. In every case 

 the rays are strong on the posterior half. The males are very like to U. nasutus, 

 Say, but are not so transverse nor of so acute an angle on the posterior margin ; but 

 the females differ very much, as they are all much inflated on the umbonial slope, 

 and look more like the female of U. iris (nobis). The young are more like U. 

 Texasensis (nobis), than nasutus, but they differ entirely in the form of the undula- 

 tions of the beaks, the Texasensis having a few concentric ones. 



Unio Forsheyi. PI. 60, fig. 182. 



Testa valde et minute tuberculata, subquadrangulari, coiapressa, subaequilaterali, postice subbiangulata; 

 valvulis subcrassis, antice' crassioribus ; natibus subelevatis, ad apices acuminatis et elegantissime per- 

 undulatis; epidermide viridi-lutea, substriata, obsolete radiata, submicante; dentibus cardinalibus sub- 

 grandibus, erectis, crenulatis, in utroque valvulo duplicibus; lateralibus rectis brevibusque; margarita 

 argentea et paulisper irideseente. 



Shell covered with small tubercles, nearly quadrangular, compressed, nearly equi- 

 lateral, subbiangular behind ; valves rather thick, thicker before ; beaks somewhat 

 raised, pointed at the tips and beautifully covered with undulations ; epidermis green- 

 ish yellow, slightly striate, obscurely rayed and slightly shining ; cardinal teeth rather 

 large, erect, crenulate, double in both valves ; lateral teeth straight and short ; nacre 

 silver white and somewhat iridescent. 



Proc. Acad. Nat. Sci. 1859, p. 155. 



Hah. — Fayette County, Texas. Prof. C. G. Forshey; and Alabama, J. G. Anthon}'. 



My cabinet and cabinets of Prof. Forshey and Mr. Anthony. 

 Diam. - 8, Length 1/7, Breadth 2 inches. 



Shell covered with small tubercles, nearly quadrangular, compressed, nearly equi- 

 lateral, flattened on the sides, subbiangular behind and rounded before ; substance of the 

 shell rather thick, thicker before ; beaks somewhat raised, pointed at the tips and beauti- 

 fully covered with a double row of small angular undulations ; ligament small and 

 brown ; epidermis greenish-yellow, slightly striate, obscurely rayed and somewhat 

 shining, with distant and rather distinct marks of growth ; umbonial slope raised into an 

 angle and furnished with a series of tubercles becoming more distant apart as they recede 

 from the point of the beaks ; posterior slope slightly raised, furnished with a series of 

 nearly parallel rows of elongated tubercles passing in curved lines from the umbonial 

 slope to the margin, and with a yellow ray on each valve ; anterior slope furnished 

 with nearly parallel rows of tubercles up to the margin ; cardinal teeth rather large, 

 erect, crenulate, double in both valves; lateral teeth straight, short and lamellar; 

 anterior cicatrices distinct and well impressed ; posterior cicatrices confluent and but 



91 



