THE TERTIARY FORMATIONS OE VIRGINIA. 365 



are in a state of remarkably perfect preservation, and present an unu- 

 sual variety of species, belonging to the genera Venus, Pecten, Pectun- 

 culus, Madra, Crassatella, Asfarte, Ostrea, Corhula, Turritella, Oliva, 

 Fissurella, and others. Their interior is chiefly filled with the green 

 sand. 



2. A layer of ferruginous sandstone; and 



3. A stratum of diluvium. 



Locality at Cockle-Shell Branch, Northumberland County. 



Here the strata are : 



1. A bed of marl, consisting of common sand mixed with green 

 sand, and containing a large number of shells. 



2. A layer of a bright green indurated sandy clay, approaching to 

 the hardness of rock, and containing innumerable impressions of Vene- 

 ricardia granulata, Pectunculus pulmnatus and P. subovatus, and other 

 shells of rare delicacy and beauty, but entirely devoid of the shells 

 themselves. 



3. A bed of common sand, largely mixed with green sand. 



4. A layer of sandy clay, with markings resembling shells. 



5. Diluvium. 



Locality two and a half Miles above the Mouth of HuWs Creek, Northumberland County. 



1. At the base of the steep bank of the creek, and within a few 

 inches of the water's edge, occurs a ledge of ferruginous rock, contain- 

 ing an immense number of shells, closely cemented together, as well 

 as the casts of sim.ilar fossils. These are chiefly Perna max., Venus 

 and Pecten. This ledge is two feet thick. 



2. A stratum of yellowish sandy clay, of the same thickness, abound- 

 ing in I'erna max., in a very friable condition. 



3. A light blue marbled clay, ten feet. 



4. Coarse diluvium. 



The foregoing detailed account of various localities in the neck will, 

 it is hoped, give a correct idea of the generally prevailing order and 

 fossil contents of the meiocene strata in this district, and at the same 

 time exemplify the principal varieties presented in them, as regards 



