64 Cretaceous. 



and other places in Nebraska (Fort Pierre Group), Ptychoceras mor- 

 toni, Fusus subtiirrltus, now Pyrifusus subturritus, F. interiextics, now 

 P. ititerfextus, Xylophaga elegantula, now Turnus elegantuhis, X. 

 stimpsoni^ now T. stimpsoni; from (Fox Hills Group), near the mouth 

 of Heart river, Fusus vaughni; and from other parts of Nebraska, 

 Fusus (?) scarboroughi, now Fasciolaria scarboroughi, Pholadomya 

 subventricosa, Cyprina cordata, now Sphceriola (?) cordata, C com- 

 pressa, C subtumida, C. ovata, Pectunculus subimbricatus, now 

 Axincea subimbricata, Ostrea translucida, Hemiaster hionpJireysanus; 

 from the mouth of Judith river, Vitrina obliqua, Planorbis amplexus. 

 Helix occidentalism now Hyalina occidentalism H. viirinoides, now 

 a. vetusta, 3Ielania omitta, now Goniobasis omitta, 31. subtortu- 

 osa. now G. subtortuosa, 31. sublwvis, now G. sicblwvis, 31. invenusta, 

 now G. invenusta, Unio danai, IT. deweyanus, IT. subspatulatus., 

 Ostrcea glabra; from the Fort Union Group, Lignite beds at Fort 

 Berthold on the Missouri river, Planorbis fragilis, now P. 2)l'^inocon- 

 vexus, 3Ielania tenuicarinata, now Goniobasis tenuicarinata, M.. 

 warrenana, now Hydrobia warrenana; from the Fort Benton Group, 

 at the mouth of Vermilion river, Serpuld tenuicincta; from the Da- 

 kota Group, near the mouth of Vermilion river, Solen dakotensis, now 

 Phorella dakotensis, and Cyprina arenaria, now Cyrena arenaria. 



The rocks* of the Lower Cretaceous, in Mississippi, consist princi- 

 pally of stratified sand, mixed with a large proportion of silicate of 

 iron or glauconite, which imparts to it a greenish color of different 

 hues, and has given origin to the very appropriate name of greensand. 

 The indurated greensand is generally' full of fossils. It is exposed in 

 the western part of Tishamiugo, eastern part of Tippah, northwestern 

 part of Itawamba, northeastern part of Pontotoc, and northeastern part 

 of Lowndes county. 



The Upper Cretaceous has sometimes been called the rotten lime- 

 stone, and occupies a larger area than the lower division. It occupies 

 part of Kemper, Noxubee,. Lowndes, Ocktibbeha, Chickasaw, Monroe, 

 Pontotoc and Itawamba counties. This division is also highly fossil- 

 iferous where well exposed. The estimated thickness of the whole is 

 placed at from 1,200 to 1,500 feet. 



Dr Leidyf described, from Columbus, Miss., Hadrodus prisons; from 

 Nebraska, Phasganodus dirus^ and from the greensand of New Jersey, 

 Pycnodus robustus. 



'■' Geo. of Miss. 



t Proc. Acad. Nat. Sci., vol. 9. 



