214 Tertiary. 



entirely, to be replaced by mijlions of Orbitoides imbedded in a semi- 

 indurate mass of carbonate of lime, interspersed at times with similai"- 

 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 (0. nu-pera) at Vicksburg, 

 does not alter the case, for the undoubted 0. mantelU 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 0. 7nanteUi, and its companions, Pecten poulsoni 

 and Ostrea vickshurgensis. Of course, the coral had its favorite 

 haunts — the mollusks theirs. There is nothing surprising in the fact, 

 that whei'e one abounds, the others are usuall}^ 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, as a subordinate feature. 

 Its inconsiderable thickness readily explains its entire absence at 

 many points, where, stratigraphicallj^ it ought to appear. 



Prof. E, D. Cope* described, from the Miocene of Charles count}-, 

 Maryland, Eschrichtius cephalus, Rhahdosteus latiradix., Squalodon 

 memo, Aetohatis profundus, Myliohatis gigas, M. 2^'^fchyodon, M. vi- 

 Gomicanus, Raja dux., N'otida7ius plectrodon, Galeocerdo Icevissimus, 

 Sphyrna magna, Trionyx cellulosus, Theco^champsa contusor, T. seri- 

 codon, Orycterocetus crocodilinus, Priscodelphimis acutidens, Esch- 

 richtius leptocentrus, Squalodon jyroterims, and Galera macrodon. 



T. A. Conradf described, from the Eocene of Texas, Venericardia 

 mooreana; from the Miocene of the Eastern and Southern States, Pleu- 

 romeris decemcostata, Mactra contractu, 31. virginiana, Lucina den- 

 sata, Cardium emmonsi, Mercenaria percrassa, Mulinia parilis, 

 Semele carolinensis, Ahra nuculiformis, Corbula curta, Pecten tricari- 

 natus, P. yorkensis, Sycotypus pyriformis, Cylichna, virginica, Zizy- 

 phinus hriani, Z. punctatus, Neverita densata, A^. emmonsi, Ptycho- 

 salpinx, scalaspira, Paranassa granifera.^ Bursa, centrosa, and Busy- 

 con dumosum. Prof. Gill described, from North Carolina, Sycotypus 

 elongatus. 



In 1868, Prof. J. W. DawsonJ offered the following reasons, to show, 



* Proc. Acad. Nat. Sci. 



t Am. Jour. Conch., vol. iii. 



X Acadian Geology. 



