1887] The Perissodactyla, : 999 
lophus is from the summit of the Eocene in North America, or 
from the Diplacodon beds. 
_ As but one genus of TRIPLOPODIDÆ is known, its origin and 
_ probable descendants only can be referred to. It may very 
readily have been derived from Heptodon, with which it agrees 
 indental formula. The loss of the heel of the last inferior molar 
and of the fifth anterior digit would metamorphose Heptodon 
into Triplopus. Two species are known, both from the upper 
division of the Bridger Eocene. A possible third species is from 
the Diplacodon bed (Prothyracodon S. and O.). 
E i> pes is 
SF 
À 
Y 
IG. 13, Skull of Tyiplopus cubitalis Cope, from the Bridger Eocene les 
Cing, three-quarters natural size; right side. Original; from the “Report U. S. 
l ve Surv. Terrs.,” vol. iii. Fig. a, superior molars with deciduous premolars; 
^ third and fourth superior premolars, 
a The CaNopip# include genera which have lost the superior 
: canine teeth, and have thus come to resemble the rhinoceroses. 
te known genera resemble these animals also in the reduction 
“tlie number of the incisors, and in one genus at least a dermal 
"n was present. The two genera known differ as follows: 
No dermal horn; .. Canopus Cope. TO. 
A dermal frontal homp. iii ccsvessesresdecenasnassoyensse „Dihoplus Brandt. — 
*tossesor 
a> family constitutes the transition between the Lophiodon- 
“™ group of the Lophiodontidæ by Heptodon or Hyrachyus, 
