276 



10. Cyclas ovalis NoMs. Mss. 

 Cabinet of the B. S. N. H, 



Shell. Small, pellucid, fragile, transparent, equilateral, some- 

 what elongated, not much inflated ; outline of the valves oval ; 

 beaks small, rounded, not prominent ; lines of growth light and 

 regular ; color in some specimens of a light yellow, in others of 

 a greenish yellow ; hinge margin very gently rounded ; teeth 

 small; cardinal teeth double. 



Long. 0.26 ; lat. 0.24 ; diam. 0.17 inches. 



Localities. Oswego and Greenwich, N. Y. (Ingalls.) Co- 

 lumbus, O. (Anthony.) 



This seems to be a common shell. I have frequently received 

 it from Ohio, as the C. partumeia, with which shell it is not possi- 

 ble to confound it. Its very oval form renders it not only attract- 

 ive but also distinct from any other species. Compared to the C. 

 cardissa, it differs in being less globose and in being more elon- 

 gated. Compared to the C. truncata, it is less inflated, more 

 elongated, and the margins are more rounded. 



11, Cyclas securis NoMs. Bost. S. N. H. Proc. iv. 160. 

 Annals of the N. Y. Lyceum of N. H. v. 218, pi. (J. 



Cabinet of the B. S. N. H. 



Animal., of a bright pink color, imparting a pinkish hue to the 

 shell ; siphons of about the same length, rather small, and of a 

 pink color ; foot long and very retractile. 



Shell. Vide Bost. S. N. H. Proc. iv. 160. 



Localities. Cambridge, Mass. (Nobis.) GJroton, Mass. 

 (Lewis.) Vermont, (Adams.) 



This species is allied to th'e C. truncata, and to the C pellu- 

 cid a ; under the description of C. truncala we have compared it 

 with that shell. Compared to C. pellucida, it is smaller ; it dif- 

 fers in color ; it is less deep, less broad ; the posterior extremity 

 is less broad, and the anterior one is more narrow ; the beaks 

 are a little larger. Compared to the C. rosacea., the margins are 

 more spherical, the valves are more full, the hinge margin is 

 more straight, and the beaks are larger. 1 have found this shell 



