228 
ELEMENTS OE GEOLOGY. 
and chiefly of the latter. The general elevation of this plain 
bordering the Atlantic does not exceed 100 feet, although it 
is sometimes several hundred feet high. Its width in the 
middle and southern states is very commonly from 100 to 
150 miles. It consists-, in the South, as in Georgia, Alabama, 
and South Carolina, almost exclusively of Eocene deposits; 
but in North Carolina, Maryland, Virginia, Delaware, more 
modern strata predominate, of the age of the English Crag 
and faluns of Touraine.* 
Fig. 148. Fig. 149. 
Fulgur canaliculatus. Maryland. Fusus quadricostatus, Say. Maryland. 
In the Virginian sands, we’ find in great abundance a spe¬ 
cies of Astarte (A, undulata^ Conrad), which resembles close¬ 
ly, and may possibly be a variety of, one of the commonest 
fossils of the Suflblk Crag (A. Omalii) ; the other shells also, 
of the genera Natica^ Fissiirella^ Artemis^ iMcina^ Charria^ Pec- 
tunculiis^ and Pecten^ are analogous to shells both of the Eng¬ 
lish Crag and French faluns, although the species are almost 
all distinct. Out of 147 of these American fossils I could 
only find thirteen species common to Europe, and these occur 
partly in the Suflblk Crag, and partlj^ in the faluns of Tou- 
raine; but it is an important characteristic of the American 
group, that it not only contains many peculiar extinct forms, 
such as Fusus quadricostatus^ Say (see Fig, 149), and Venus 
tridacnoides^ 2 i\)VLndi 2 inX in these same formations, but also some 
shells which, like Fulgur carica of Say and F, canaliculatus 
(see Fig. 148), Calyptrma costata^Venus mercenaria^ Lam.*, 
Modiola glandula^ Totten, and Pecten magellanicus^ Lam., 
are recent species, yet of forms now confined to the western 
side of the Atlantic—a fact implying that some traces of the 
beginning of the present geographical distribution of mollus- 
* Proceed, of the Geol. Soc., vol. iv., pt. iii., 1845, p. 547. 
