THE NATIONAL INSTITUTION. 191 



Bivalves. Bivalves. 



Mytilus hamatus. Say. Solen ensis. Lam. 



Nucula limatula. Say. Venus merccnaria, Lam. 



Nucula acuta, Conrad. 

 The entire thickness of the tertiary clays has not been determined, but it has 

 been ascertained that they sink to a very considerable depth, enough to convey the 

 idea of a vast period of time elapsing between their origin and final deposition. 

 Deep harbors and bays seem to have been filled up by the very gradual accumula- 

 tion of fine silt or mud; generations of shells were entombed in frequent succession, 

 until the harbors, bays, or part of the ocean itself shrinking into shallow lagoons, 

 no longer furnished the conditions necessary to their increase, and myriads of oys. 

 ters took possession of their deserted beds. There is no pause, no interruption to 

 this ceaseless mutability. Our harbors and our bays must, in the lapse of ages, be 

 filled up by the unfailing influx of silt ; our present beds of oysters be converted 

 into dry banks of shells. New bays will succeed to those which we now behold ; and 

 other lagoons will encroach upon the sea. Whoever attentively examines the lo- 

 cality last described, on the Potomac river, will be forcibly reminded of the mutabihty 

 of the present features of our earth ; he can read distinctly the history of the 

 past, and anticipate, in a measure, the annals of futurity, the new order of things, 

 the relative condition of sea and land yet to be, long after he has passed away, and 

 his name, his influence, his labors having left no more trace of his existence than 

 the "baseless fabric of a vision." 



In Silliman's Journal of Science and Arts, I have noticed a spot on the Neuse 

 river, in North-Carolina, of more than ordinary interest, in consequence of the quan- 

 tity of bones of land animals which are mingled with the upper tertiary shells. 

 This place is about fifteen miles below Newborn, on the left bank of the river, and 

 the two formations of medial and upper tertiary are in juxtaposition. The former, 

 when I visited the spot, was concealed from observation, the excavations having 

 been filled up, and the beds being nine feet beneath the level of the Neuse. Mr. 

 Benners, who owned the land, informed me that all the bones were above this for- 

 mation, mixed with the upper tertiary shells. These remains are nearly all water 

 worn, black and sUicified, and have evidently been transported from a distance, pro- 

 bably carried by ice down the ancient Neuse, and dropped among the shells of the 

 upper tertiary period. The bank of the river is here not in any part more than 

 twenty feet high. The surface of the fossilliferous portion is very irregular, rising 

 in a few places to the height of ten feet above the river. Its visible part consists 

 of a mixture of sand and clay, in which arc imbedded immense numbers of Mactra 

 lateralis, and abundance of Solen ensis, towards the top of the stratum. The shells 

 with two exceptions, are such as now exist on the southern coast of the Atlantic, 

 and in the Gulf of Mexico, and the evidence of a climate very similar to that of 

 the locality last described on the Potomac, is perfectly satisfactory. The Gnatlto. 

 don occurs here, aud the whole group is very well represented in the Gulf of Mexico 



at the prusent day. 



List of Fossil Shells at Bcnners's, 



Univalves. Univalves. 



Buccinum IriviUatum, Say. Fulgur canaliculatus. 



