78 PLEIOCENE FOSSILS. 



Cyrena densata occurs in the Meiocene of Virginia. In South-Carolina, more perfect 

 specimens are found, but the valves are always separated. 



The occurrence of this fossil is an interesting evidence of the existence of estuaries 

 during the Pleiocene period. 



D'Orbigny has united under Cyclas, the genera Cyrena and Pisidium. 



Plate XX. Fig. 14, Interior of right and exterior of left valve, natural size. 



Locality. Darlington District. 



Museum, College of Charleston. 



The genus is represented in the Oolite, and is found in great numbers in the fauna of 

 the present period. 



VMERIM. 



VENUS KILEYI.-Con. 

 Plate XXI. Fig. 8. 



Venus Rileyi, Con., Foss. Ter. For., p. 9, pi. 6, fig. 1. 



V. testa ovata, sub-ventricosa, crassa, incequilaterali, concentrice rugosa; latere anali 

 elongato; latere buccali brevi; lunula ovata. 



Description. Shell ovate, somewhat ventricose, thick; anal side elongated; buccal 

 side short; lunule ovate. 



This is one of the largest species, and often attains to double the dimensions of the 

 individual figured. It is distinguished from other species by being much more equilateral. 



When the recurved lines of growth are preserved, it is rough on the exterior, but where 

 these are removed the surface is rather smooth and concentrically striated. The beaks are 

 compressed, and there is a broad obsolete fold on the anal margin. 



