281 



lighter shade, a zone of bright yellow bordering the inferior and 

 part of the lateral margins. 



Long. 0.55 ; lat. 0.50 ; diam. 0.33 inches. 



Localities. New Orleans, La. (Blaldeman.) 



This beautiful species is, by its spherical form, totally different 

 from any other known shell. Prof. Haldeman, who discovered 

 this species at New Orleans, has found but one single valve. 



20. CYCLAS FURCATA Rqfinesque. Mss. 

 Cabinet of the Ac. Nat. Sc. 



Shell. Ovate, full, somewhat orbicular, strong ; posterior extre- 

 mity somewhat angular ; anterior and interior margins rounded, 

 nearly equilateral ; beaks large, well rounded, but not prominent, 

 having a tendency towards the anterior; hinge margin very 

 much curved ; cardinal teeth small ; two united in one ; lateral 

 ones large, sharp ; surface heavily and regularly striated ; color 

 uniform dark chestnut-brown, interior bluish. 



Long. 0.49 ; lat. 0.43 ; diam. 0.33 inches. 



Locality. Ohio ? (Rafinesque.) 



The specimens from which this description was made, kindly 

 sent to me by Prof. Haldeman, were labelled by Rafinesque's 

 own hand, but I have not been able to find their species in any 

 work, and conclude it must have been in manuscript. 



21. CYCLAS STAMINEA Conrad. Amer. Journ. xxv. 342. 

 Cabinet of the B. S. N. H. 



Shell. Oval, ventricose, inequilateral, with numerous regular, 

 prominent, concentric lines ; beaks prominent ; anterior and 

 posterior ends nearly equally rounded ; hinge margin curved ; 

 cardinal teeth nearly obsolete ; lateral ones distinct and promi- 

 nent ; interior dark blue. 



Long. 0.39 ; lat. 0.34 ; diam. 21 inches. 



Locality. Alabama, (Conrad.) 



This is a well marked species, not easily to be confounded 

 with any other. 



