APPENDIX 



Aet. L. — A New Family of Homed Dinosauria, from the 

 Cretaceous; by O. 0. Marsh. (With Plate XL) 



During the past season, a special effort has been made by 

 one field-party of the .U. S. Geological Survey, to explore the 

 Laramie formation, more particularly in Dakota and Montana. 

 In this work, important collections of vertebrate fossils have 

 been secured, and among them are remains of some new 

 Dinosaurs of much interest, one of which is briefly described 

 below. 



Ceratops monta?ius y gen. et sp. no v. 



The present genus appears to be nearly allied to Stegosaurus 

 of the Jurassic, but differs especially in having had a pair of 

 large horns on the upper part of the head. These were sup- 

 ported by massive horn-cores firmly coossified with the occipital 

 crest. The latter are probably attached to the parietal bones, 

 but, as the sutures in this region are obliterated, they may be 

 supported in part by the squamosals. 



The horn-cores in the type specimen are sub-triangular at 

 base, but nearly round in section in the upper half. Their 

 position is represented approximately in the figures of the 

 accompanying plate. These horn-cores are slightly hollowed 

 at the base, but are otherwise solid. The exterior texture 

 and markings show that they were evidently covered with true 

 horns, and these must have formed large and powerful offen- 

 sive weapons. 



In position and direction, these horn-cores are somewhat 

 similar to the large posterior pair of protuberances in 

 Meiolania, one of the extinct Testudinata, and to the 

 corresponding ones of the existing Phrynosoma. The only 

 known example of similar structure in the Dinosauria is the 

 single median horn-core on the nasals of Ceratosaurus, from 

 the Jurassic. It is not improbable that there were other 

 horn-cores on the skull in the present genus, but, of this, there 

 is at present no positive evidence. A detached median promi- 

 nence resembling a horn-core was found with some similar 

 remains, but may pertain to an allied genus. 



Am. Jour. Sci.— Third Series, Yol. XXXYI, No. 216.— Dec, 1888. 

 30 



