UNITED STATES AXD NORTHERN MEXICO. 55 



from the tips to margin on each valve ; cardinal teeth compressed, erect, acuminate 

 and crenulate ; lateral teeth very long, lamellar and nearly straight ; anterior cica- 

 trices distinct, moderately small and well impressed ; posterior cicatrices confluent 

 and somewhat impressed ; dorsal cicatrices placed in the centre of the cavity of the 

 beaks ; cavity of the shell shallow and wide ; cavity of the beaks very shallow and 

 obtusely angular; nacre white or tinted with salmon color and iridescent. 



BejnarJcs. — Only two perfect specimens were sent to me for examination by the 

 Smithsonian Institution, neither with the soft parts. In outline it is closely allied to 

 U. Poeyanus (nobis), but differs in the beaks, in being of a darker color and in the 

 epidermis being striate, while the Poeyamis is minutely granulate. I name the species 

 after Capt. Pope, who collected this with other species during an expedition in New 

 Leon, Mexico. 



Anodonta Henrtana. pi. 66, fig. 198. 



Testa lasvi, oblonga, inflata, ad basim et antic6 compressa, subc-equilaterali, postic6 trunoata; valvulis per- 

 tenuibus ; natibus depressis, planulatis, ad apices minute et irregulariter undulatis ; epidermide niti- 

 da, vel lutea vel luteo-viridi, obsolete radiata et vittata ; margarita caeruleo-alba et vald^ iridescente. 



Shell smooth, oblong, inflated, compressed at the base and before ; nearly inequi- 

 lateral, truncate behind ; valves very thin ; beaks depressed, flattened, minutely and 

 irregularly undulate at the tips; epidermis bright, yellow or yellowish green, obsoletely 

 rayed and banded ; nacre bluish white and very iridescent. 

 Proc. Acad. Nat. Sci. 1857, p. 102. 



Eah. — Matamoras and Tamaulipas, Mexico. L. Berlandier, M. D. 



My cabinet and cabinet of Smithsonian Institution. 

 Diam. 1, Length 1-5, Breadth 2-8 inches. 



Shell smooth, oblong, inflated, compressed at the base and before, nearly equilateral, 

 truncate behind and obtusely angular before ; substance of the shell very thin, sub- 

 transparent ; beaks depressed, flattened, minutely and irregularly undulate at the 

 tips ; ligament very long, thin and light brown ; epidermis bright, polished, yellow 

 or yellowish green, obsoletely rayed and spotted, and with distant marks of growth ; 

 umbonial slope inflated and rounded ; posterior slope raised into a carina and furnished 

 with a few obscure lines from the beaks to the margin ; anterior cicatrices confluent, 

 large and very slightly impressed ; posteiior cicatrices confluent, large and scarcely 

 perceptible ; dorsal cicatrices small and placed in the centre of the cavity of the 

 beaks ; cavity of the shell deep and wide ; cavity of the beaks so shallow as to be 

 scarcely perceptible ; nacre bluish white and very iridescent. 



Sofl Parts. — Branchial xiterus filled through the whole length of the outer branchiae. 

 Branchinc rather large, rounded below, inner ones rather the larger. Mantle very thin, 

 thicker and double at the edges. Branchial opening rather small, with numerous 



