176 PROCEEDINGS OF 



temporaneous deposit at Claiborne, a mere trace of this gonus was all I could find 

 during a protracted investigation of the fossils. If we suppose, then, the lowest 

 bed at Claiborne to have been deposited in the ocean, we must infer this to have 

 been elevated until if was cut oft' by a beach, and thus converted into a lagoon, 

 because the group of oceanic shells was suddenly interrupted, and the OstrecB began 

 to congregate upon them in the land-locked and calm water. These, in their turn, 

 ■were as suddenly banisliod by the sinking of the coast, which converted their 

 harbor into the open sea, and restored the oceanic shells to their original po- 

 sition. 



Although I believe the rise of land to have been generally by insensible degrees, 

 through the agency of the crystallizing force acting throughout primary or grani- 

 tic rocks, yet for this sudden interruption of groups from an oceanic to an estuary 

 character, some other explanation seems necessary. Two theories only present 

 any claim to our attention : one is, that a sand bar might have been suddenly 

 formed by a violent tempest, which permanently remained to protect the shells in 

 the lagoon; and the other, and perhaps more probable solution, is, that during an 

 earthquake the land may have been suddenly elevated. The sea was cut off from 

 its original beach by a bar, previously under water at all tides, but now constituting 

 an embankment, which the ocean might never again be destined to pass. Of this 

 conversion of sea into land-locked water, we see proofs every whore throughout the 

 three tertiary divisions, but of the conversion of the latter into the former, or sink- 

 ing of the land, 1 am acquainted only with the solitary but interesting example at 

 Claiborne. I know not in what estimation others may hold this phenomenon as 

 evidence of the sinking of the land, but to my mind it appears as conclusive as the 

 perforations of Uthodomi on the columns of the temple at Puzzuoli, so admirably 

 illustrated by Lyell. 



Classification of Tertiary Formations. — It is doubtful, in the comparison of ter- 

 tiary deposits, whether the relative amount of recent and extinct species may not 

 be carried to an extreme injurious to science, especially before all the fossil as well 

 as the recent forms shall be obtained. In the strata above the eocene, especially, 

 is great care requisite in this mode of comparison, as the groups vary so continually 

 in localities separated by an inconsiderable interval, that the fossils of the one shall 

 be nearly or quite all of extinct species, and those of another shall embrace several 

 existing forms. Nor can there bo any doubt of the synchronous nature of those 

 deposits, when wo refer to tho medial tertiary formation, because, taking a gene- 

 ral view of the palteontology of the region, it is found to characterize a single era 

 in the clearest and most satisfactory manner. Even when we trace the deposits 

 in their horizontal continuation throughout a long lino of coast, like that of the 

 Chesapeake bay, we begin at one extremity, with a certain class of shells, which 

 gradually drop some and acquire other forms, as wo proceed towards tho opposite 

 termination of the bods, where there will be found scarcely a species in common 

 with those at tho spot whcro we commenced observation. In my first explorations 

 in Maryland, I was greatly surprised to find a group of shells on tho Choptank river, 

 near Easton, which scarcely hold a fossil in common with the localities I had pre- 

 viously studied on tho western Poninsulii, yet I could not doubt tlic contemporaneous 

 origin of all these beds ; and I subsequently found nr:.rlv i)ir same group on the ahora 



