n POST-PLEIOCENE FOSSILS. 



separated this period from its successor; and that served, apparently, in each case to mark 

 the close of one period and the commencement of another. 



The next in order and third of the series, is named the Mesozoic or middle life, and its 

 fossils belong to that middle or intermediate class of animals between the most ancient 

 and recent forms. These also in turn became, like their predecessors extinct, and were 

 succeeded by a later creation. 



The next and last age is named the Cainozoic — recent life- — and by some authors called the 

 Tertiary, or third grand division, and in which we discover, for the first time, the created 

 forms that are to be the cotemporaries of man. 



These divisions, or grand divisions, as they may be called, are again sub-divided into 

 minor periods or formations; the first, consequently the lowest and oldest in the series of 

 the Cainozoic or Tertiary, is called Eocene, for in it we find representatives of the 

 dawn or commencement of that creation; a few species, two or three per cent, only, hav- 

 ing been perpetuated down to the present time. 



In the Meiocene, the next in age, a larger number of species are found whose existence 

 is thus prolonged. 



In the Pleiocene, more recent, a majority of the fossils are of recent species; and at 

 last, in the Post-Pleiocene — the most recent — ninety -five per cent, or nearly all the species, 

 continue to the present time. This last, the Post-Pleiocene, is an extensive formation in the 

 low or flat country of South Carolina and is included in a belt extending from the sea coast 

 about ten miles inland, and occupies depressions in the great marl bed of the Eocene 

 period. 



Three distinct formations or beds are here supposed to belong to this age. First the ma- 

 rine beds, composed of a gray sandy clay in which are imbedded innumerable small shells, 

 sometimes very comminuted, but of species now common and living on the coast ; many 

 of the large shells are preserved in the position they occupied when living, having both 

 valves entire and perfect, and presenting the appearance of having been destroyed suddenly 

 by an avalanche of sand. 



The second, is the blue or pluff-mud bed, composed of a stiff blue clay, containing silici- 

 ous pebbles, and masses of conglomerates, water-worn and boulder-like, but no angular 

 blocks, and includes remains of marine and terrestrial animals. These pebbles and rolled 

 conglomerates contain casts of the fossils common to the marl of the Eocene bed upon which 

 the blue mud rests, and it has been ascertained that the silicious conglomerates are fragments 

 of the marl, broken off, we infer, by the action of waves, and rolled upon the beach of a 

 Post-Pleiocene sea ; they afterwards were imbedded in the blue mud, lost all their lime or 

 calcareous particles, and became silicified. 



The third or upper bed includes the peaty deposits, yellow sands and clays, which over- 

 lie the pluff-mud. 



Sections of the three most important localities may be represented in the following 

 tables : 



