April 4. 1873.] ~' h) [Xarib. 



ON THE GIGANTIC MAMMALS OF THE AMERICAN EOCENE. 



By Professor O. C. Marsh. 



(Abstract of a paper read before the American Philosophical Society, 

 April ±th, 1873.) 



The recent publications of this Society contain a number of papers by 

 Prof. Cope on a group of Eocene mammals which I have called Dinocerata, 

 and previously described in the American Journal of Science.* In a 

 communication to this Society, December 20th, 1872, I pointed out some 

 of the errors made by Prof. Cope in his descriptions of these animals, 

 and I have since corrected many others elsewhere. \ As it is important 

 to have the true characters and affinities of the Dinocerata, as well as the 

 facts relating to their discovery, placed on record, I desire now to call 

 the attention of the Society to a number of points in which Prof. Cope's 

 various papers on this subject need correction : 



1st. The name Tinoceras, Marsh, antedates Eobasileus, Cope, and the 

 family name, Tinoceratidcs, also has priority over Eobasiliida. 2d. The 

 name Loxolophodon is preoccupied, and heuce should not be applied to 

 this genus. 3d. Eobasileus cornutus, Cope, is a synonym of Tinoceras 

 y nt nd is, Marsh. E. furcatus, Cope, was based on the posterior horn- 

 cores of known species, and not on the nasal or frontal bones as Prof. 

 Cope supposed. 4th. The genus Dirtoceras, Marsh, is quite distinct from 

 Uintatherium, Leidy, although perhaps nearly related. It differs essen- 

 tially in the position of the occipital condyles in the more anterior posi- 

 tion of the posterior horn-cores, and in the structure of the upper true 

 molars. 5th. The mammals of the above genera constitute a distinct 

 order, Dinocerata, which approaches the Perissodactyls rather than the 

 Proboscidians. (3th. There is no evidence, in the osteological characters, 

 of a long proboscis, and much against it. 7th. The Dinocerata have no 

 under incisors, and the teeth so called by Prof. Cope are canines. 8th. 

 The nasal bones are much elongated, and the anterior horn-cores are 

 on these bones and not on the frontals. 9th. The frontal bones do not 

 extend in front of the premaxillaries, and they do not support horns or 

 processes at both extremities. 10th. The middle pair of horn-cores are not 



* Vol. II, p. 35, July, 1871; Vol. IV. Erratum, Sept. ,1872. and pp. 322,323,343, Oct. ,1672. 

 i Am. Jour, Sci.,Vol. V. pp. 117,293 and 310, 1873. Also Am. Naturalist , Vol. VII. pp. 52, 



1-1.. aud 217. 



