THE ORDER DINOCERATA. ; 121 
20. ON THE ORDER DINOCERATA (Marsx).* 
Ir is very seldom that specimens are now obtained, either fossil or Page 267. 
recent, of mammalian forms that have, provisionally at least, to be 
placed in a new order by themselves, on account of the presence of 
peculiarities hitherto quite unknown and unexpected. Such, how- 
ever, is the case with a large series of fossils which have been, 
within the last two years, obtained from the Eocene deposits of 
Wyoming in North America. Our chief source of information 
respecting these remains consists of a series of papers by Professor 
O. C. Marsh, of Yale College, abstracts of which have recently 
appeared in “The American Journal of Science,’ and in “The 
American Naturalist.” Professor E. D. Cope has also published 
several papers on the subject, and some excellent photographs of one 
of the most important forms sent by him to this country it has been 
my good fortune to see. Professor Leidy has also named one of the 
genera. Most of my information is obtained from the papers by 
Professor Marsh on the Order Dinocerata, together with the critical 
- remarks made by him on Professor Cope’s descriptions, which I have 
also by me. 
Dinoceras mirabilis is the name given by Marsh to a huge ungulate 
animal, of which there is an almost complete skeleton in the museum 
of Yale College. Its size must have been very nearly that of a full- 
grown elephant, as the length of the skull of a closely allied genus 
was a little more than a yard. The skull was peculiarly long and 
narrow, and supported three pairs of horn cores in rows, on its 
superior surface. The anterior pair were situated on the anterior 
ends of the nasal bones; they were short, conical, and directed nearly 
straight upwards. The median pair were conical prolongations 
upwards from the maxillaries; they were longer and more cylindrical 
than those on the nasals, and the fangs of the huge canine teeth 
entered their bases. The posterior pair, the largest, were very pecu- 
liar, being extensions upwards from near the middle of large lateral 
longitudinal crests, which were formed by the occipital, parietals, and Page 268. 
frontal bones. The dentition was peculiar; the upper incisors 
were deficient, and the premaxille consequently small. The upper 
canines formed huge downwardly directed tusks, nearly straight, but 
directed somewhat backwards. These, after a gap equal to their 
* “Journal of Anatomy and Physiology,” VII. pp. 267-270. June, 1873. 
oS a 
