LNITKli STATICS AND XulMIIKliX MKXiru 3^ 



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

 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 fT, nasiiU,)^, 

 Say, but are not so transverse nor of so acute an angle on the po.sterior 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 nnsutus, but they differ entirely in the form of the undula- 

 tions of the beaks, the Te-i-'iteimx having a few concentric ones. 



Unio FoKSHEvr. PI. (50, fig. ]82. 



Testn, valde et minute tuberculata, subquadrangulari, compressa, subaequilaterali, postice subbiangulata; 

 valvulis subcrassi.s, antice cra.ssioribus; iiatibus subelevatis, ad apices acuiiiinatis et elegantissimi'- per- 

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

 grandibus, erectis, crenulatis, in utroqne valvuln duplicibus; lateralibus recti.s brevibuM|ue ; inorgarita 

 argentea ct paulispor iridcscente. 



Shell covered with small tubercles, nearly quatlrangular, 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. 1S59, p. L55. 



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



My cabinet and cabinets of Prof. Forshey and Mr. Anthon}^ 

 Diam. -8, Length Iw, 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 di.^tant 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 di.stinct and well impressed ; posterior cicatrices confluent and but 



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