184 GEOLOGICAL SURVEY 
Natica duplicata, 
Saxicava distorta, 
Fusus cinereus, Anomia ephippium, 
Dentalium dentalis, Ostrea Virginiana. 
This makes the proportion of recent and extinct species about 13 per cent. The list, of course, 
is not a complete one, but is taken just as the fossils are described in Mr. Conrad’s book. 
In 160 species, which [ have from the Miocene of Virginia, the following recent species are found. 
Cardita granulata, 
Dispotea rugosa, 
Pyrula carica, 
fe canaliculata, 
Natica heros, 
“  — duplicata, 
Crepidula fornicata, 
id plana, 
Buccinum trivitatum, 
e obsoletum, 
Fusus cinereus, 
Scalaria clathrus, 
Iispotea rugosa, 
ie corrugata 
Lucina divaricata, 
if squamosa, 
‘é crenulata. 
Lucina contracta, 
Anomia ephippium, 
O. Virginiana, 
Artemis acetabulum, 
Cytherea Sayana, 
Dentaliuwm dentalis, 
Solen ensis, 
Cardita granulata, 
Venus mercenaria, 
Nucula limatula, 
“ ye 
p7 oxrvma, 
eg acuta, 
Lutraria canaliculata, 
Mactra lateralis, 
We have here 29 species, or about 18 per cent. of the entire number. 
The largest collection of fossils from North Carolina was that made by Mr. Hodge ;* it comprises 
about 80 species, of which 27 are now living. This makes the proportion in that State nearly 34 
per cent. of recent species. 
In Maryland and Virginia Tertiary fossils have been collected with some diligence, but in North 
Carolina our collections are yet too small to admit of any very reliable conclusions; yet, judging 
from the grouping of the organic remains, I am persuaded that the beds of that State will range 
with those of South Carolina, in the Pliocene. 
There is one source of uncertainty that must, for some time yet, attend all our comparisons of 
recent and extinct species—it is our imperfect and very limited knowledge of the Fauna of the 
whole southern coast, where, it is obvious, we must look for the living representatives of our fossils. 
Mr. Conrad’s explorations on the coast of Tampa Bay show how much remains yet to be done, 
before we may, with entire certainty, pronounce species extinct. 
When we psssess such a work on the southern coast as “Gould’s Invertebrate Animals of Mas- 
sachusetts,” our generalizations, founded on the proportions of recent and extinct species, will be enti- 
tled to far more confidence. Besides the identification of species, we must study the habits of the 
molluscous inhabitants of the shells, as affected by climate ; for I suppose that mollusca common to 
the coasts of Massachusetts and South Carolina would have their habits greatly modified, to com- 
* Reports Am. Ass. Geol. and Nat. 1843. 
