86 OBSERVATIONS ON NAIADES, 



My Cabinet. 

 Diam. -9, Length 1-4, Breadth 1*8 inches. 



Shell subtriangular, angular behind and rounded before, covered 

 with small rough tubercles except in a furrow which passes from the 

 beak obliquely to the basal margin which is there arcuate ; the tuber- 

 cles along the posterior slope arrange themselves into a series of undu- 

 lations as far as the beaks ; substance of the shell thick ; beaks slightly 

 prominent : ligament short and thick ; epidermis brown and wrinkled ; 

 cardinal tooth rather large, slightly elevated and widely cleft in the 

 left valve, single and emerging from a pit in the right valve ; lateral 

 teeth small, slightly curved in a direction over the cardinal teeth ; pos- 

 terior and anterior cicatrices both distinct ; dorsal cicatrices situated 

 on the under part of the cardinal tooth within the cavity ; cavity of the 

 beaks deep and angulated ; nacre very pearly and iridescent. 



Remarks. — The asper is more covered with tubercles than any spe- 

 cies I have seen, these being small and numerous. It bears some re- 

 semblance to U. luberculatus (Barnes), and U. lacrymosus (Nobis.). 

 It differs from the tuherculatus in outline, and in possessing a furrow 

 passing from the beaks to the basal margin. It differs from the 

 lacrymosus in the form of the tubercles (which in that species so 

 much resemble flowing tears) and in the roughness and colour of the 

 exterior. 



Unio Fabalis. Plate X. fig. 16. 



Testa subellipticd, transversa, incequilaterali, crassd; valvulis crassis ; radiis 

 capillaribus undantibusque ; dentibus cardinalibus parvis ; lateralibus brevibus, 

 crassis, et in termino postico auctis ; margaritd alba et iridescente. 



Shell subelliptical, transverse, inequilateral, thick ; valves thick; rays hair-like 

 and undulating; cardinal teeth small; lateral teeth short, thick and enlarged towards 

 the posterior end; nacre pearly white and iridescent. 



Hab. Ohio river, T. G. Lea. 



