LOCAL DEVELOPMENT OF THE CERATOPS BEDS. 129 



and the position of all important localities where he collected vertebrate 

 fossils was of the greatest value to us. A part of Mr Hatcher's collection 

 of invertebrates and plants having come into our hands, it was evident 

 that important data might be obtained there for correlation with beds 

 in other regions by means of these classes of organisms. With his map 

 in hand it was an easy matter to locate our collections with reference to 

 the vertebrates which have been obtained there. 



The area examined by us extends along both sides of Lance creek 

 from Little Lightning creek to Doegie creek, and from Buck creek on 

 the east to about the mouth of Box creek on the west, the extreme dis- 

 tances being about 16 miles from north to south and 25 or 30 miles from 

 east to west. 



On the northern and eastern borders of this area the non-marine beds 

 are sharply upturned and overlie with apparent conformity fossiliferous 

 marine Cretaceous strata, of which several hundred feet are exposed 

 where the streams have made favorable cuttings. The lowest beds ex- 

 posed are the soft, bluish shales of the Fort Pierre, with frequent cal- 

 careous concretions containing characteristic invertebrates. Small col- 

 lections from this horizon were obtained one mile east of Lance creek 

 and on Buck creek near the old corrals, yielding the following species : 



Avicula fibrosa, M. and H. Dentalium gracile, H. and M. 



Inocerarnus cripsii, Mantell. Anchura sp. 



Gervillia subtortuosa, M. and H. Baculites ovaius, Say. 



Cucullsea shumardi, M. and H. Scaphites nodosus (Owen). 

 Protocardia subquadrata (E. and S.). 



The Fox Hills and the beds immediately overlying contain several 

 massive sandstones, which together form a prominent ridge, usually bear- 

 ing a few pine trees, and rising from 200 to 300 feet above the plain formed 

 by the Fort Pierre shales. The succession and relations of the beds can 

 be best shown by two local sections taken from the best exposures ex- 

 amined at localities about eight miles apart. The thicknesses were rather 

 hastily estimated by pacing distances and measuring dips, but as the 

 beds are very well exposed the errors are probably not great. 



The first section is about two miles east of Lance creek, where the fol- 

 lowing strata were seen in ascending order : 



1. Sandy clay shales, with occasional bands of brown sandstone; thick- 



ness unknown, as the base is not exposed. 



2. Yellowish gray argillaceous sandstone, with large concretions contain- 



ing Veniella humilis, Sphasriola, and other Fox Hills fossils, dip 20 



degrees northwest, thickness 30 feet. 



3. 



Brown micaceous sandstone 20 " 



4. Gray thin-bedded sandstone 20 



(< 



