10 DESCRIPTION OF NEW 



Unio arctior. Plate IV. fig. 1 0. 



Testa angulato-elliptica, valde transversa, compressa ; valvnlis subtenuibus ; natibus com- 

 pressis el undulalis ; dentibus cardinalibus parvis; lateralibus longis; margarita alba et 

 salmonis colore tincta. 



Shell narrow-elliptical, very transverse, compressed; valves ratlier ihin ; beaks 

 compressed and undulated; cardinal teeth small; lateral teeth long; nacre white and 

 salmon colour. 



Hab. Ohio River, near Cincinnati. T. G. Lea. 



My Cabinet. 

 Cabinet of P. H. Nicklin. 

 Cabinet of Professor Vanuxem. 

 Cabinet of William Hyde. 

 Diam. -7, Length ri. Breadth 2-3 inches. 



Shell narrow, elliptical, very transverse, subangular behind, flattened 

 on the sides; substance of the shell rather thin; beaks compressed, un- 

 dulated; ligament rather long and slender; epidermis dark brow'^n, 

 wrinkled ; cardinal teeth very small ; lateral teeth long, straight, and- 

 enlarged at posterior end ; anterior cicatrices distinct ; posterior cica- 

 trices confluent; dorsal cicatrices situated on the plate between the 

 cardinal and lateral teeth ; cavity of the shell very shallow ; cavity of 

 the beak shallow and subangular; nacre white, salmon colour, and 

 sometimes purple. 



Remarks. — I have for some years been in doubt if this should be 

 separated from the gibbosus of Barnes, of which it has generally been 

 considered a variety. After proper examination, believing it to be dis- 

 tinct, I propose to separate it from that species. It certainly very 

 closely resembles the gibbosus, but may at once be distinguished by its 

 being a smaller shell, and possessing much less substance. The gibbo- 

 sus is generally purple ; this species is usually white or salmon colour, 

 but sometimes purple. 



