279 



found buried in the mud. Dr. Mighels has found it in Maine, 

 living mostly in crevices of decayed timber floating in ponds. 



The prolificity of this species surpasses that of all others, 

 especially in the warm months. Mr. Hyde took fifty young 

 ones out of a single specimen. Say. 



16. CYCLAS JAYENSIS Nobis. Bost. S. N. H. Proc. iv. 157. 

 Cabinet of the B. S. N. H. 



Shell. Vide Bost. S. N. H. Proc. iv. 157. 



Locality. Lake Superior, (Agassiz.) 



This beautiful and rare species somewhat resembles the 

 C. parlumeia ; it is, however, less inflated, the posterior extre- 

 mity is more abrupt, and the anterior one less rounded. In out- 

 line it has some affinity to the C. pellucida^ but the beaks are 

 larger, and the valves are more inflated. 



17. CYCLAS EBURNEA Anthony. 

 Cabinet of the Ac. Nat. Sc. 



Shell Compressed, fragile, nearly equilateral ; posterior ex- 

 tremity abrupt ; anterior one somewhat rounded, much narrower 

 than the posterior margin ; inferior margin rounded ; beaks not 

 large, like tubercles, slightly inclined towards the anterior ; 

 lines of growth very fine and regular ; color light gray, inter- 

 spersed with yellow, a narrow zone of yellow round the mar- 

 gins ; beaks yellow, faint perpendicular lines of the same color 

 running from the discs to the inferior margin ; hinge margin 

 nearly straight ; cardinal teeth united, small ; lateral ones not 

 prominent. 



Long. 0.40 ; lat. 0.37 ; diam. 0.20 inches. 



Locality. Arkansas, (Anthony.) 



This species is somewhat allied to the C. Jayensis ; it differs, 

 however, in being much less inflated ; the posterior margin is 

 less abrupt, and the anterior one more rounded ; the beaks are 

 smaller and less prominent, and the hinge margin is straighter. 



Compared to the C. partumeia, it is less full ; the beaks are less 

 prominent, the margins are generally less rounded ; it is broader 

 and more equilateral. Compared to the C. pellucida, it is less 

 elongated, more inflated; the beaks are not so distant, and the 



