NATURAL SCIENCES OF PHILADELPHIA. 21 



Descriptions of new CRETACEOUS FOSSILS from Nebraska Territory, collected 

 by the Expedition sent out by the Government under the command of Lieut. 

 John Mullan, IT. S. Topographical Engineers, for the location and construc- 

 tion of a Wagon Road from the sources of the Missouri to the Pacific 

 Ocean.* 



BY F. B. MEEK AND F. V. HAYDEN. 



The collections containing the fossils described in this paper, were obtained 

 along the Missouri River at various localities between Fort Benton and points 

 140 to 150 miles below the Fort. The new forms here for the first time made 

 known, are all labelled " Chippewa Point," which is some twenty odd miles 

 below Fort Benton. There are also in the collection from this locality, and ap- 

 parently from the same rock, some fine specimens of our Inoceramus umbonatus 

 and /. fragilis, Hall and Meek. The presence of the latter species, and the 

 affinities of several of the new forms, indicate that these fossils all come from 

 No. 2 of the Nebraska Cretaceous series, which is known to be extensively 

 developed in that region: fragments of one or two of the new species at least, 

 have certainly been found in that horizon at other places. As we have no sec- 

 tion of the strata exposed at this locality, however, we are without the means 

 of knowing whether or not these fossils all came from the one bed. Iudeed, 

 some of them being quite peculiar, and very unlike anything hitherto known 

 in our Nebraska series at other localities, it is barely possible there may be a 

 member here of the Cretaceous not previously recognized elsewhere in this 

 region. 



There are also in the collection from the same place as the above, a number 

 of good specimens of Atrypa reticularis ; they are labelled " Chippewa Point, 

 300 feet above the level of the river." These are of Devonian or Upper Silu- 

 rian age, and were doubtless broken from boulders, or other erratic masses, 

 brought by drift agencies from some distant northern locality, and of course 

 have no connection with the geology of this immediate vicinity. 



At another locality, ninety miles below Fort Benton, a specimen of our Tan- 

 credia Americana, and a few other bivalves, were obtained, though we do not 

 know whether they were found in situ or loose. They evidently belong to the 

 same beds occurring at the mouth of Judith River, farther up, which we have 

 elsewhere referred with doubt to the Dakota Group, (No. 1) of the Nebraska 

 Cretaceous series. That this bed is Cretaceous, is proved by the occurrence in 

 it of of Baculites, as well as by the affinities of its other fossils, excepting the 

 Tancredia, which would alone point to a lower horizon. Its exact position ir. 

 the Cretaceous series still remains doubtful. 



The collection also contains from other places 125 to 150 miles below Fort 

 Benton, specimens of Oslrea sublrigonalis, Evans and Shumard, and of the fol- 

 lowing species elsewhere described by us : Corbicula [Cyrena] cytheriformie, 

 Corbula permidata, Vivipara Conr adi and V. trochiformis ; all of which belong to 

 the Fort Union Group, (brackish water and lower Tertiary deposits) of that 

 region. Some of these were probably obtained from loose masses. Good speci- 

 mens of Baculites compressus, Say, were likewise collected near one of these 

 latter localities. 



Figures and more extended descriptions of the new species here indicated 

 are to be prepared by us for publication in Lieut. Mullan's final Report. 



* The fossils described in this paper were collected by Mr. John Pearsall, who acted 

 as naturalist of Lieut. Mullan's expedition. 



1862] 



