[Read before the American Association for the Advancement of Science, Portland 
Meeting, August 20, 1873.] 
On some Extinct Types or Hornep Prrissopactytes. By 
Epwarp D. Corr, of Philadelphia, Penn. 
Ir is well known that the type of Mammalia of the present 
period, which is preéminently characterized by the presence of os- 
seous horns, is that of the Artiodactyla ruminantia. At the meet- 
ing of the Association of last year, held at Dubuque, I announced 
that the horned mammals of our Eocene period were most nearly 
allied to the Proboscidians. I now wish to record the fact, as I 
believe for the first time, that the Perissodactyles of the inter- 
mediate formation of the Miocene embraced several genera and 
species of horned giants, not very unlike the Hobasileus and Uinta- 
therium in their armature. 
While exploring in connection with the United States Geological 
Survey of the Territories, I discovered a deposit of the remains 
of numerous individuals of the above character, which included 
among other portions crania in a good state of preservation. 
Most of these skulls are nearly or quite three feet in length, and 
mostly deprived of their mandibular portions; these are quite 
abundant in a separated condition. The crania represent at least 
six species, while the mandible represents a condition distinct 
from that of Titanotherium or any allied genus, viz.: I., 0; C., 1; 
P.M.,3; M.,3. The teeth diminish rapidly in size anteriorly, and 
there is no diastema behind the canines, whose conic crowns do 
not exceed those of the premolars in length. To the genus and 
species thus characterized I have elsewhere given the name of 
Symborodon torvus. 
One of the crania, referred to under the name of Miobasileus 
ophryas, is characterized by its strong and convex nasal bones 
(108) 
