APPENDIX. 



Art. LX. — The Skull of the Gigantic Cerato-psidce y* by 

 O. C. Marsh. (With Plate XII.) 



The huge horned Dinosaurs, from the Cretaceous, recently 

 described by the writer, f have now been investigated with 

 some care, and much additional light has been thrown upon 

 their structure and affinities. A large amount of new material 

 has been secured, including several skulls, nearly complete, as 

 well as various portions of the skeleton. 



The geological deposits, also, in which their remains are 

 found have been carefully explored during the past season, and 

 the known localities of importance examined by the writer, to 

 ascertain what other fossils occur in them, and what were the 

 special conditions which preserved so many relics of this unique 

 fauna. 



The geological horizon of these strange reptiles is a dis- 

 tinct one in the upper Cretaceous, and has now been traced 

 nearly eight hundred miles along the eastern flank of the Rocky 

 Mountains. It is marked almost everywhere by remains of 

 these reptiles, and hence the strata containing them may be 

 called the Ceratops beds. They are fresh-water or brackish 

 deposits, which form a part of the so-called Laramie, but are 

 below the uppermost beds^referred to that group. In some 

 places, at least, they rest upon marine beds which contain 

 invertebrate fossils characteristic of the Fox Hills deposits. 



* Abstract of a paper read before the National Academy of Sciences, 

 Philadelphia, November 14, 1889. 



f This Journal, vol. xxxvi, p.. 477, December, 1888 ; vol. xxxvii, p. 334, April, 

 1889; and vol. xxxviii, p. 173, August, 1889^. 



Am. Jour. Sci.— Third Series, Vol XXXVIII, No. 228.— Dec, 1889. 

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