APPENDIX. 
Notice of New Tertiary Mammals; by O. C. Marsu. 
IN addition to the extinct Mammals already described by the 
writer, the Museum of Yale College contains some interesting 
remains of this group from the various Tertiary deposits of the 
Rocky Mountain region. Nota few of these specimens are new 
to science, and some of the more important are here described. 
Orohippus agilis, sp. nov. 
_ Additional specimens of this genus fully justify its separa- 
tion from Anchitherium, and likewise show that it holds a most 
interesting intermediate position between that genus and the 
less specialized mammals of the Palaotherium type. 
differs essentially from Anchitherium in having four functional 
digits in the manus, in having the first premolar nearly as large 
as the second, and in the absence of an antorbital fossa. The 
Skull is elongated, and equine in its proportions. The orbit was 
not enclosed behind. There were three upper true molars, and 
our premolars. The radius and ulna were separate, and the 
latter bone is stouter than in Anchitherium. 
preserved indicate, moreover, a somewhat larger animal, which 
nearly equalled a fox in size. “ 
Measurements. 
Space occupied by upper molar series,..-..--------.--- £0: ee: 
Space occupied b upper true molars, ies be ee 
Antero-posterior Seton of penultimate upper molar,_. 8° 
Sverse. diameter... 5 nig soos neeeme ee hes cee Bee scans 9° 
Transverse diameter of distal end of BOOT UR wis es 20° 
Transverse diameter of proximal end of radius, .-------- 17: 
Transverse diameter of distal end on articulation, ---.-_- 12°4 
ransverse diameter of distal end of ulna,_---.-.--.- --- 5°6 
ngth of third metacarpal, 55°5 
The known remains of this species are all from the Eocene of 
Wyoming. 
Colonoceras agrestis, gen. et sp. nov. 
Tn its cranial characters and dentition, this genus resembles 
Most nearly Hyrachyus Leidy, and Helaletes Marsh. It differs 
* This Journal, vol. iv, p. 207, Sept., 1872. 
