CYRENA. 21 



I have not been able to identify this species, which Mr. Hanley 

 informs me is very rare, the shell labelled as such in the cabinet 

 of Mr. Cuming, he says is not the true C. placens. 



II A beautiful and rare species, of which I have never seen but 

 my own specimen and that in the Jardin des Plantes at Paris. 

 The sulci are close and regular, and the outline of the shell, 

 although not very unlike that of C. radiata, is convex in front 

 of the beaks, thus rendering the front extremity broad and some 

 what obtuse. &quot; Hanley. 



I have reason to believe that this species is closely allied to 

 V. fontaineii. 



16. Cyrena fontaineii, CARPENTER. Shell trigonal, solid, com 

 pressed, inequilateral ; ante 

 rior side short, rounded ; pos 

 terior narrow ; acute and an 

 gular at extremity ; beaks 

 small, acute, eroded ; striae 

 fine, regular, epidermis smooth, 

 chestnut-brown ; interior of 

 the valves light-blue ; hinge- 

 margin curved, thick ; cardi 

 nal teeth large, unequal, di 

 vergent, the anterior ones bi 

 fid ; lateral teeth unequal, an 

 terior proximate, conical, pos 

 terior distant, elongated, com 

 pressed. C. fontaineii. 



Long. 1.66; Lat. 1.40; Diam. 0.80 inches. 



&quot; 41; &quot; 35; &quot; 20 mill. 

 Nab. South America. (Cabinets of Cuming, Jay and Prime.) 



Cyclas fontaineii, D ORB. Voy. Amer. 1844, 569, pi. 83, f. 14, 15. 

 Cyrena fontaineii, CARP. Mazatlan Shells, 1857, 114. 



Compared with C. olivacea, with which this species has been 

 confounded, its outline is more regular, it is smaller, more com 

 pressed, the beaks are smaller and more acute, the epidermis is 

 smoother and of a different color. A rare species. 



11. Cyrena acilta, PRIME. Shell trigonal^ oblique, transversely 

 elongated, very inequilateral, somewhat compressed, solid ; anterior side 

 short, rounded at end ; posterior side produced, angular at end ; beaks tu 



