0. C. Marsh — Skull of Torosaurus. 83 



the inside, is especially noticeable. In figure 1, of this plate, 

 the long, slender, right squamosal of Torosaurus, with its 

 smooth outer border, is well represented. In figure 2 is seen 

 the same bone of Sterrholophus, with a serrate outer margin, 

 and smooth inner surface, also shown in figure 5. Next, in 

 figure 3, is the small, short squamosal of Ceratops, nearly 

 bisected by its deep quadrate groove. The free sculptured 

 border of both the parietal and squamosals of Triceratops is 

 clearly shown in both figures 4 and 6, especially in the latter, 

 where the contrast with the corresponding parts in figure 5 is 

 noteworthy. 



Three other generic names have been applied by Cope to 

 remains of Ceratopsidm found in this country, namely : Aga- 

 thaumas, Polyonax, and Monoclonius* The first of these 

 was based on part of a skeleton without the skull, found in 

 Wyoming. The second name was given to various fragments 

 from Colorado, including parts of horn-cores, regarded as ischia, 

 but these may all be the same generically as the preceding 

 specimen. The third name, Monoclonius, was used for a 

 skeleton from Montana, with parts of the skull and teeth 

 preserved. This animal was one of the smallest of the 

 group, while the other remains pertained to reptiles of larger 

 size, but not of the gigantic proportions of those more recently 

 described. So far as can be judged from the descriptions and 

 figures of the type specimens, the three generic names just 

 cited cannot be used for any of those previously mentioned 

 in this article. A comparison of the principal characters will 

 place this beyond reasonable doubt. 



In the type of Agathaumas, the remains best preserved are 

 in the pelvic region, which according to Cope possesses the 

 following features. The ilium has no facet nor suture for 

 the pubis at the front of the acetabulum, and the base of the 

 ischium is coosified with the ilium. There are eight, or per- 

 haps nine, sacral vertebrae, with the neural spines of the first 

 five mere tuberosities. The diapophyses are in pairs, and the 

 last sacral vertebra is reduced and elongate. These characters, 

 and some others found in the description cited, are certainly 

 distinctive, but do not apply to any of the allied fossils 

 described by the writer. Portions of the type specimen, more- 

 over, are in the Yale Museum, as well as other remains from 

 near the same locality. The fossils described as Polyonax, 

 and other similar specimens collected in the same region, 

 afford at present no evidence for separation from Agathaumas. 



* Cretaceous Vertebrata, p. 58, Plates IV, V and VI; p. 63, Plates II and III, 

 1875. Also Proceedings Philadelphia Academy, p. 255, 1876. and American 

 Naturalist, p. 154, 1886, and p. 715, Plates XXXIII, and XXXIV, for 1889, 

 issued in 1890. 



