THE HEAD OP CHESAPEAKE BAY. 395 



twenty-one ovoidai processes, or what Mr. Blake calls 

 conical processes. It is considerably convex on one 

 side, which leads to a belief that it is a grinder of the 

 upper jaw ; the convex side corresponding with the arch 

 of the zygoma and alveolar circle. Its weight, after the 

 loss of its roots and gelatinous matter, is more than ten 

 pounds. 



At upper Marlborough, on the Patuxent river, there 

 is a stratum of rock of a gray shore-sand, filled with 

 shells of an univalve mollusca, which seems to be a buc- 

 cinum. The specimens I possess are very beautiful. 



I possess also the moulds, in indurated clay, of that 

 spiral shell which resembles a cork screw. In these 

 the covering has perished, and the earthy core alone 

 remains. Some of them have been flattened and distort- 

 ed by compression. 



The fossil remains in this region, bordering on the 

 quehannah and the Chesapeake, afford proofs like those 

 already stated of a deposite from inland floods since the 

 oceanic strata were formed. There is an extensive field 

 for further research, which the sons of science in Mary- 

 land will hasten to explore. 



The effects of the breach by the Potomac river, upon the land 

 below the Falls. 



The region with which I am more particularly ac- 

 quainted, is the District of Columbia. Washington, the 

 seat of the general government, is situated in lat. 38 53' 

 N. seventeen miles below the Great Falls of the Poto- 

 mac, where the locks have been constructed, and about 



