﻿EXOTIC UNIONID^E. 269 



Unio Averyi. PL 44, fig. 149. 



Testa sulcata, subtriangulari, subventricosa, inaequilaterali, postice obtuse - angulata, antice subrotundata ; 

 valvulis crassis, antic6 crassioribus ; natibus subproinmentibus ; epidermide rufo-fusca, eradiata ; 

 dentibus cardinalibus subcrassis, suberectis, valde crenulatis ; lateralibus crassis, subrectisque ; mar- 

 garita alba et iridescente. 



Shell sulcate, subtriangular, rather ventricose, inequilateral, obtusely angular 



behind, rounded before ; valves thick, thicker before ; beaks ra.ther prominent ; 



epidermis reddish brown, without rajs ; cardinal teeth rather thick, nearly erect, 



very crenulate ; lateral teeth thick, and nearly straight ; nacre white and iridescent. 



Unio Averyi, Lea. Proe. Acad. Nat. Sci. ; 1859, p. 281. 



Hdb. — Chumnagua River, Isthmus of Darien. Mr. Frederick Avery, per J. G. 

 Cooper, M. D. 



My cabinet and cabinet of William Cooper, Esq., Hoboken, N. J. 

 Diam. 1-2, Length 1-6, Breadth 2-3 inches. 



Shell sulcate, subtriangular, very ventricose, inequilateral, obtusely angular 

 behind, rounded before; substance of the shell thick, very much thicker before; 

 beaks rather prominent ; ligament thick and rather short ; epidermis reddish brown, 

 rather rough, without rays and with rather distant, indistinct marks of growth ; 

 umbonial slope rounded; posterior slope rather wide; cardinal teeth rather thick, 

 nearly erect, very crenulate single in the right and double in the left valve ; lateral 

 teeth thick, nearly straight, rather short and obtuse at the posterior end ; anterior 

 cicatrices distinct and very deeply impressed ; posterior cicatrices distinct and well 

 impressed ; dorsal cicatrices well impressed and placed under the plate behind the 

 cardinal teeth ; cavity of the shell rather deep- and rounded ; cavity of the beaks 

 shallow and rounded ; nacre white and iridescent. 



Remarks. — There were two specimens only of this species sent to me by J. G. 

 Cooper, M. D., who informs me that they were brought by Mr. Avery from that 

 ill-fated expedition across the Isthmus of Darien under Lieut. Strain, and were " the 

 Clams on which they partly subsisted on their journey across the Isthmus." This 

 species in outline is somewhat approaching to Unio cyrenoides, Phili.,* from Lake 

 Nicaragua, but it is not so thick, nor is it so triangular as that species, nor so high in 

 the beaks. The figure of Dr. Philippi represents the exterior as sulcate, but he does 

 not give that character in his diagnosis. Our species is but slightly sulcate, and one 

 specimen is more so than the other. In both the erosion of the beaks and sides is so 

 great as almost to debar a correct idea of its exterior. The character of the undula- 

 tions of the tips, if there be any there, of course cannot be yet determined. There are 

 few of the species indigenous to this country to which it can be compared. It is per- 



* Conchylien, vol. 3, pi. 5, fig. 1 



