0. (' Mitfxli — Characters of t) Uopsidas. 421 



front of tlu 4 acetabulum forms a broad, horizontal plate, which 



continued backward over the acetabulum, and narrowed in 



the elongated, posterior extension. Seen from above, the ilium, 



I whole, appears as a nearly horizontal, sigmoid plate. From 



the outside, as shown in the figure, the edge of this broad plate 



sen. 



The protuberance for the support of the pubis is com- 

 paratively small, and elongated. The face for the ischium is 

 much larger, and but little produced. The acetabular face of 

 the ilium is quite narrow. 



The pubis is massive, much compressed transversely, with 

 its distal end widely expanded, as shown in the figure. There 

 is no post-pubis. The pubis itself projects forward, outward, 

 and downward. Its union with the ilium is not a strong one, 

 and is similar to that seen in the pubis of Stegosaurus, as repre- 

 sented in the diagram on Plate VII, fifir. 2. 



The ischium is smaller than the pubis, but more elon- 

 gate. Its shaft is much curved downward and inward, and in 

 this respect, it resembles somewhat the corresponding part of 

 the pubis of the ostrich. There is no indication that the two 

 ischia met closely at their distal ends, and they were probably 

 united only by cartilage. 



A comparison of this pelvis with that of Stegosaurus shows 

 some points of resemblance, but a wide difference in each of 

 the elements. The pubis corresponds very closely, in its essen- 

 tial features, to the pre-pubis of Stegosaurus, but the post-pubis 

 is entirely wanting in the specimen figured. 



The characters which separate the Ceratopsia from the other 

 known orders of the Dinosauria may be briefly stated, as 

 follows : 



(1) The skull surmounted by massive horn-cores. 



(2) A rostral bone forming a sharp, cutting beak. 



(3) The teeth with two distinct roots. 



(4:) The anterior cervical vertebrae coossified with each other. 

 (5) The pubis projecting in front, and no post-pubis. 



There are various other characters, more or less distinctive, 

 but not of ordinal importance. 



For the discovery of the specimens here described, belonging 

 to this order, science is mainly indebted to the writer's able 

 -rant, J. B. Hatcher, whose genius has done so much to 

 bring to light the rare fossil vertebrates of the West. 



