AND AVES OP NORTH: AMERICA. 



249 



by Cook in the Geological Survey. of New Jersey as the Chocolate stratum. This bed 

 (lifters from the pure green-sand above it, in its containing a much larger proportion of 

 clay and sand, indications of shallower water. Near its middle is the great bed of Ostrea 

 vesiculates, also an indication of estuary enclosure. While bones are abundant through- 

 out, they are especially so near its upper surface. T suppose it, therefore, to have been 

 the slowly subsiding bottom of an area not far removed from shore. The termination of 

 the Chocolate bed, and commencement of the stratum of pure green-sand, indicates per- 

 haps a more rapid or sudden submergence to the greater depth, appropriate; to the life of 

 the Globigerinee, in whose empty shells the green-sand grains are supposed to have been 

 formed. That towards the close of this period of deposit shallower water may have cov- 

 ered the area, is suggested by the great bed of Ostrea vesicularis at that horizon. Between 

 it and the chocolate, the remains of Eteptilia are comparatively rare. 



From the above, I am much disposed to conclude that the clay and mixed green-sand 

 marls of our upper Cretaceous were deposited in a series of estuaries, whose direction fol- 

 lowed the lines of the Appalachian axis, i. e., northeast and southwest, and which were 

 protected by shore lines to the seaward. Such a shore line formed of an anticlinal of 

 Eozoic rocks, separated an estuary from the Miocene ocean in North Carolina. Its crest 

 can be seen where exposed by the denuding action of the Tar, Cape Tear and other rivers 

 and streams. 



J> 



II. The Fresh-water (Mays of the Pea Shore. 



This deposit, which I discovered to be truly fresh-water in its origin, by the observa- 

 tion of numerous species of Unio and Anodonta near its base, has been regarded by 

 Rogers and all others who have examined it up to the present time, as a member of Meek 

 and llayden's No. 1, and as lying conformably beneath the upper Cretaceous strata to the 

 southward and eastward. The most important part of the deposit consists of a heavy 

 black clay which is used for making brick, which rests on a, bed of hard laminated clay, 

 with a thin layer of iron-stone between. The clay bed at one place examined, is 25 feet 

 in thickness, and at from one to three feet from its bottom occurs a bed of fresh-water 

 mussels. These are Unios and Anodontas of six species, all of them as pointed out to 

 him by Dr. Lea, hitherto undescribed. The beds are from the top of the clay down, con- 

 formable, and have a, dip of about 25" to tin; southeast. The upper surface of the clay is 

 worn into holes, which are filled by the material of a, bed of coarse gravel of little depth, 

 which covers the whole. Above this is a bed of fine sand varying from (i to 15 feet in 

 thickness to the soil. 



AMULU. PHILOSO. SOC. — VOL. XIV.. — 68 



