48 



NEW UNIONID.5; OF THE 



rays from the beaks to the margin on both valves ; anterior cicatrices confluent, largo 

 and slightly impressed ; posterior cicatrices confluent, large and very slightly im- 

 pressed ; dorsal cicatrices placed in the centre of the cavity of the beaks ; cavity of the 

 shell somewhat deep and wide ; cavity of the beaks shallow and wide ; nacre bluish 

 white and iridescent. 



Bemarlcs.—K single specimen only was given to me by Prof. Daniels, to whom I 

 dedicate it. It is nearer to that variety of cygnea, which Pfeiffer called ponderosa, than 

 any species I have seen. It differs in the undulations of the beaks, in being higher 

 on the posterior slope and in being less ponderous. It is more compressed and darker 

 than any American species I know. The specimen before me has but three double 

 undulations on each beak. 



Anodonta Texasensis. pi. 63, fig. 191. 



Testa laevi, elliptica, inflata, ad latere rotunda, inaequilaterali, poatico subangulata; vatvulis pertenuibus; 

 natibus subprominentibus, ad apices biundulatis; epidermide dilute lutea, glabra, fulgida, obsolete 

 radiata ; margarita cseruleo-alba, diaphana et valde iridescente. 

 Shell smooth, elliptical, inflated, rounded on the sides, inequilateral, subangular 

 behind; valves very thin; beaks a little prominent, with a double row of undula- 

 tions at the tips ; epidermis pale yellow, smooth, shining, obsoletely rayed ; nacre 

 bluish white, semitransparent and very iridescent. 

 Proc. Acad. Nat. Sci. 1859, p. 113. 



jjah. Texas. W. Newcomb, M. D. 



My cabinet and cabinet of Dr. Newcomb. 

 Diam. -8, Length 1% Breadth 2 inches. 



Shell smooth, elliptical, inflated, rounded on the side, obtusely angular behind ; 

 substance of the shell very thin ; beaks somewhat prominent, with a double row of 

 rough undulations at the tips ; ligament thin, rather short and light colored ; epider- 

 mis pale yellow, inclining to brownish, and light .green towards the margin, smooth, 

 shining, very obscurely rayed, and with distant lines of growth ; umbonial slope very 

 slightly rounded, anterior cicatrices confluent and very slightly impressed ; posterior 

 cicatrices confluent ; dorsal cicatrices placed in the centre of the cavity of the beaks ; 

 cavity of the shell rather deep and rounded ; cavity of the beaks shallow and slightly 

 angular ; nacre bluish white, semitransparent and very iridescent. 



Remarks. The specimen before me is probably a half grown one, certainly not 



adult, and I have not had the advantage of examining a second. The diagnosis, 

 therefore, would not apply fully to an adull. In outline and general characteristics 

 it is nearest to decora (nobis), but differs in color of the epidermis, in the dorsal line 

 not being so straight and in the posterior slope not being raised into so high a keel. 

 It is rather roughly striate on the posterior slope, where there are three lines on each 

 valve from the tip to the posterior margin. The undulations of the beaks are finely 



