‘ 
26 Cincinnati Society of Natural History. 
entirely, to be replaced by millions of Orbitoides imbedded in a semi- 
indurate mass of carbonate of lime, interspersed at times with similar- 
ly constituted conglomeratic masses of Pecten poulsoni. He could 
not, therefore, agree to the propriety of distinguishing as separate 
divisions the Orbitoides limestone, and the Vicksburg Group. The 
occurrence of a different species of Orbitoides (O. nupera) at Vicksburg, 
does not. alter the case, for the undoubted O. mantelli occurs there also, 
in the solid rock. And there are few of the characteristic fossils of 
the Vicksburg profile, which do not, on some occasions, occur side by 
side with the O. mantelli, and its companions, Pecten poulsoni, 
and Ostrea vicksburgensis. Of course, the coral had its favorite 
haunts—the mollusks theirs. There is nothing surprising in the fact, 
that where one abounds, the others are usually scarce, or vice versa. 
He regarded the Shell Bluff Group of Conrad, or the Red Bluff Group— 
No. 4 of the Vicksburg section—which is characterized by the occur- 
rence of Ostrea georgiana, as more or less co-extensive with the Vicks- 
burg Group, and regularly associated with it, asa subordinate feature. 
Its inconsiderable thickness readily explains its entire absence at — 
many points, where, stratigraphically, it ought to appear. 
Prof. E, D. Cope* described, from the Miocene of Charles county, 
Maryland, Lschrichtius cephalus, Rhabdosteus latiradix, Squalodon 
mento, Aetobatis profundus, Myliobatis gigas, M. pachyodon, M. vi- 
comicanus, Raja dux, Notidanus plectrodon, Galeocerdo levissimus, 
Sphyrna magna, Trionyx celiulosus, Thecachampsa contusor, T. seri- 
codon, Orycterocetus crocodilinus, Priscodelphinus acutidens, Esch- 
richtius leptocentrus, Squalodon protervus, and Galera macrodon. 
T. A. Conrad+ described, from the Eocene of Texas, Venericardia | 
mooreana; from the Miocene of the Eastern and Southern States, Plew- 
romeris decemcostata, Mactra contracta, M. virginiana, Lucina den- 
sata, Cardium emmonsi, Mercenaria percrassa, Mulinia parilis, 
Semele carolinensis, Abra nuculiformis, Corbula curta, Pecten tricari- 
natus, P. yorkensis, Sycotypus pyriformis, Cylichna, virginica, Zizy- 
phinus briant, Z. punctatus, Neverita densata, N. emmonst, Ptycho- 
salpinx, scalaspira, Paranassa granifera, Bursa centrosa, and Busy- 
con dumosum. Prof. Gill described, from North Carolina, Sycotypus 
elongatus. ) 
In 1868, Prof. J. W. Dawsont offered the following reasons, to show, 
* Proc. Acad. Nat. Sci. 
+ Am. Jour. Conch., vol. iii. 
{ Acadian Geology. 
