FRESHWATER AND LAND SHELLS. 63 



My Cabinet. 

 Cabinet of Dr Kirtland. 

 Cabinet of Judge Tappan. 

 Cabinet of Mr Hyde. 

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



Shell obovate, rather inflated, inequilateral, dilated behind, subalate; 

 umbonial slope rounded, inflated ; substance of the shell thin and trans- 

 parent behind, opaque and thicker before; beaks somewhat prominent, 

 furnished with double undulations; ligament rather short and slender; 

 epidermis yellowish brown, with dark rays, more numerous on the 

 portion behind the umbonial slope ; cardinal teeth lamellar, curved out- 

 ward, single in the right and double in the left valve; lateral teeth aci- 

 cular; single in both valves, and nearly straight ; anterior cicatrices 

 distinct; posterior cicatrices confluent; dorsal cicatrices placed on the 

 base of the cardinal teeth ; cavity of the shell deep and rounded ; cavity 

 of the beak small and angular; nacre somewhat salmon coloured. 



Remarks.— Dr Kirtland found this shell near Hollidaysburg, on the 

 Juniata, where he obtained it last autumn ; and to his kindness I owe 

 the specimen in my cabinet. In outline it resembles U. modiolifor- 

 mis (nobis), but cannot be easily confounded with that shell, being less 

 inflated, less obovate, and more carinate. In the teeth it differs also, 

 and is peculiar. The specimens which have come under my notice 

 have the lateral teeth single in both valves ; in the left valve there is a 

 slight disposition in one of the specimens to duplication. The nacre 

 of the shell is very iridescent and satin-like, the border dark ochre 

 brown -• this causes the stages of growth to be distinct. 



It is remarkable that, being an inhabitant of the Schuylkill, there 

 should have been but a single specimen taken, that river having been 

 almost daily searched by so many active zoologists. 



I name it after my friend, Judge Tappan, of Ohio. 



