8 DESCRIPTION OF NEW 



Unio FisHERiANUs. Plate IV. fig. 8. 



Testa scalenia, obliquo-iransversa, compressd, valde inaquilaterali ; valvulis tenuibus; na- 

 tibus compressis; dentibus cardinalibus lamelliformibus ; lateralibus longis subcurvisque; 

 margarita purpurea. 



Shell scaleniform, obliquely transverse, compressed, very inequilateral; valves thin ; 

 beaks compressed ; cardinal teeth lamellar ; lateral teeth long and somewhat curved; 

 nacre purple. 



Hab. Head of Chester River, Md. Mr Thomas Fisher. 



My Cabinet. 

 Diam. '6, Length 1-1, Breadth 2-7 inches. 



Shell rounded before and acutely angular behind, obliquely trans- 

 verse, compressed, very inequilateral ; substance of the shell thin : 

 beaks flattened and placed near the anterior margin ; umbones flattened : 

 umbonial slope elevated; ligament thin and short; epidermis dark 

 brown, smooth ; cardinal teeth lamelliform, rather conical, widely 

 cleft in the left valve ; lateral teeth long and somewhat curved ; ante- 

 rior cicatrices distinct ; posterior cicatrices confluent ; dorsal cicatrices 

 placed in the centre of the cavity of the beaks; palleal impression im- 

 perceptible ; cavity of the shell very shallow ; cavity of the beaks very 

 small ; nacre purple. 



Hemarks. — This belongs to that group of Uniones of which the 

 nasutus (Say) is the type. It differs from that species in being more 

 compressed, in being more angular posteriorly and in being apparently 

 without rays. In outline it approaches the Grayaniis and Shepardia- 

 nus (nobis), but cannot be confounded with either of them. 



I owe this species to Mr Thomas Fisher, who brought it from Ches- 

 ter River five or six years ago. 



