AP PER Dis. 
Art. XXVIIL—Notice of New Equine Mammals from the 
Tertiary Formation ; by O. C. MARSH. 
of 
others throw considerable light on the forms already made 
nown by previous investigations. In the present communi- 
cation some of the more important results obtained are briefly 
perented, those relating to the genealogy of the modern horse 
Ing of special interest. 
Orohippus Marsh. 
This Journal, iv, p. 207; v, p. 407, 
represented by three species of the genus Orohippus, the main 
characters of which have already been pointed out by the 
Posterior tubercle of the molars is wanting, The first lower 
premolar was small, and the rest of the Seer molar series 
closely resemble those in Anchitherium. There is long distema. 
1€ canine is large, and near the incisors. The crowns of the 
grinders are very short, and without cement. The dental 
formula is as follows: 
; 3 ee | fg SB 
Incisors 3 canines 5, premolars 7, molars —. 
The skeleton of Orohippus, in its general features, is decidedly 
equine, and this is ly ceatiael in t ie limbs. The 
ee oieg has a prominent acromial process, which is compressed 
and decurved, as in some of the carnivores. The humerus is 
Short and stout: - ‘Tis head: is large, and the bicipital groove 
AM. Jour. Sct.—Tarrp Serres, Vor. VII, No. 39.— 1874. 
15a 
