; OF SOUTH CAROLINA. 183 
The following table exhibits the relative proportion of extinct and recent species contained in 
this list. 
; No. of species. | Species recent. | Per cent. 
Brachiopodases2 cui4s22 25.482 cues © eee 4 
Pup CO BHROTONOGS <2 © a oo ita an Sa Sse = any 39 3 
3 Lamellibranchiata ----....._--- SA ay | eee 
Sa@IntipCuidea to] se neo tice ne toes Alsooe — ; 
; = 3 
LT ee Se See ee 190 lees 
Q } 
The number of recent species is somewhat greater. There are two or three undetermined species 
of Trochus which, I believe, are recent. Cardium sublineatum, Con. will turn out to be C. citri- 
num, (serratum,) which is occasionally found on the coast of North and South Carolina. Infundi- 
bulum depressum, Say. I. centralis, Con. was described as a recent species, but I apprehend that it 
was washed from the P. Pliocene beds along the coast, where it occurs abundantly. I have there- 
fore excluded it from the recent species of this list. 
As it stands, the proportion of recent to extinct species is nearly the same as that known to exist 
in the Norwich Crag and Sub-Appenine beds, which are recognised as Older Pliocene by English 
Geologists. 
Although there is no reason whatever to suppose that the proportion of recent species will not 
always be very considerable in these beds, yet, in generalizing, it must not be forgotten that this is 
the first list, of any extent, that has been made of the fossils of South Carolina, and that the exist- 
ence of the beds from which it is taken was barely known when this survey was commenced by 
Mr. Ruffin. Future investigations will, doubtless, by enlarging the list of species here given, alter 
these proportions, but the general result will, I think, remain the same. 
Of the eighty-seven recent species of the list, two—Natica heros and Cytherea Sayana—belong 
to the coast north of the Delaware. Dispotea rugosa and D. corrugata are only found living on 
the coast of South America. About sixty-three species are, at present, inhabitants of the coast of 
South Carolina; the rest are found recent on that of Florida, and two or three are common to the 
seas of the West Indies. 
It appears that as we proceed from North to South, the proportion of recent to extinct species 
becomes greater. If this be so, it would seem that the cause of the extinction of species in the 
United States was a gradual one, proceeding slowly from North to South. 
The species from the New Jersey Miocene are not numerous enough for comparison ; but, in 170 
species, described by Mr. Conrad, from Maryland, the following 22 recent species occur. 
Buecinum trivitatum, Cytherea Sayana, 
ss lunatum, Artemis acetabulum, 
obsoletum, Lucina contracta, 
Pyrula carica, “  erenulata, 
“  canaliculata, Venus Mortoni, 
Scalaria clathrus, “mercenaria, 
Natica heros, Nolen ensis, 
