Tertiary Strata of the Atlantic Coast. 107 
It sometimes happens that the proportion of extinct species of 
‘Testacea is much the same in two or more localities, whilst the shells 
generally ‘are specifically distinct, and it is impossible to assign any 
limits to that portion of time which may have elapsed between the 
deposition of any of these when they occur near each other as is the 
case with those alluded to, but if the members of a formation are 
widely separated, the fossil must often differ specifically. We be- 
lieve that little, if any, change has taken place among the inhabit- 
ants of the ocean since the dawn of their history, in the annals of re- 
corded time, but formerly, as now, species may have been wafted by 
currents on the log, sea weed or other extraneous substance, and 
become naturalized on shores remote from their original localities. 
We must be content with our ability to classify the grand divisions 
in chronological order, without hoping to ascertain the periods of 
time which may have intervened between the minute subdivisions of 
formations. ‘That lines of demarcation can be drawn between most 
fossiliferous strata by distinctive zoological characters, few will doubt, 
and between the two grand divisions of the tertiary series of this 
country, this line is so obvious and broadly marked, that he who runs 
may read, if he is at all acquainted with organic remains, for so far 
as a comparison of about two hundred Eocene fossils, with as many 
of the Pliocene, will enable us to decide, no one species of shell is 
common to both, whilst the former contains a few secondary fos- 
stls. ‘These facts are the more interesting, as they are just the re- 
verse of what has been remarked of the European equivalents. 
In a late number of the Journal, my friend Mr. Croom, gives a 
very interesting notice of the ‘“ marl pits” on Mr. Benners’ planta- 
tion, on the Neuse river, below Newbern. Since the publication of 
that article, Mr. Croom has politely sent me a collection of the or- 
ganic remains of these “ marl pits,” which prove them to belong to 
the newer Pliocene era. ‘They consist of the remains of land animals 
mixed with marine shells, which are numerous in species, vastly 
abundant, and nearly all referrible to existing mollusca of our coast ; 
some of them are still brilliantly colored; and retain their natural 
polish ; of sixty seven species, only five are extinct or unknown; 
only eight occur on the southern coast of FJorida and in the Gulf of 
Mexico, and the remainder inhabit the coasts of the middle and 
southern states. I think it highly probable that these fossils are su- 
perimposed on the medial Pliocene, and that some of the extinct 
species are derived from older strata. A few specimens are water 
