The American Naturalist. 



[February, 



Marsh's field work in the Ceratops beds. In a total of three and 

 one-half days field work he seems to have found sufficient time 

 to " carefully explore " the geological deposits of the Ceratops 

 beds and to trace them for "eight hundred miles along the 

 eastern flank of the Rocky Mountains," besides making num- 

 erous other observations of scientific interest. 



Of the many interesting vertebrate fossils described by Pro- 

 fessor Marsh from the Ceratops beds, those from the Denver 

 locality were secured by Messrs. Cross, Eldridge and Cannon, 

 and those from Wyoming and Montana by the writer or men 

 in his party, with one exception only, namely, the type of 

 Hadroxmru* bremceps, which was received at New Haven many 

 years ago, the locality on the label accompanying it being 

 given as Bear Paw Mountains, Montana, which is of course in- 

 correct, it doubtless is from the vicinity of Cow Island. With 

 this one single exception I can confidently state that all the 

 material described by Professor Marsh as from the Laramie or 

 Ceratops beds of Wyoming is, without exception, from Con- 

 verse Co., and was found within an area not exceeding fifteen 

 miles in width from east to west by thirty miles in length 

 from north to south ; and all the material described by him as 

 from Montana, with the one exception mentioned, was found 

 on the Missouri River between the mouth of Arrow Creek, just 

 above Judith River, and the mouth of Cow Creek, some forty- 

 five miles below, and never back farther than ten miles from 

 the Missouri. It will thus be seen that the actually known 

 area of the Ceratops beds is indeed very limited, and from these 

 areas we should exclude certainly, the Judith River or upper 

 Missouri and very likely the Black Butte locality in southwest- 

 ern Wyoming. The beds of the former certainly and those of 

 the latter almost certainly, belong to an older horizon than 

 those of the Denver or Converse Co. localities ; the latter 

 may be considered as the typical locality for the Ceratops beds. 

 All of the dinosaurs from the Judith River country are smaller, 

 less specialized forms than those from the Converse Co. and 

 Denver localities, as has already been observed by Marsh. 



Marsh's statements that the Ceratops beds are below the up- 

 permost beds referred to the Laramie and that they rest upon 



