O. C. Marsh— Vertebrate Life in America. 307 
are comparatively abundant in deposits of this age on the 
Atlantic Coast. The most interesting remains of this order, yet 
found, belong to the Zeuglodontide, which are carnivorous 
whales, and the only animals of the order with teeth implanted 
by two roots. The principal genera of.this family are Zeuglodon 
and Squalodon, the former genus being represented by gigantic 
forms, some of which were seventy feet in length. 
Saurocetes, which includes some small animals of this group, has 
been found in South America. The Dolphin family (Delphinc- 
de) are well represented in the Miocene, both on the Atlantic 
and Pacific Coast. The best known genus is Priscodelphinus, o 
tiary, and with them in the earlier beds, various Ziphioid forms 
have been found. The toothless Balenide are only known 
with certainty as fossils from the later Tertiary and more 
recent deposits. 
The Sirenians, which appear first in the Eocene of the 
related to our living species. In the Tertiary of Jamaica, 
skull has been found which indicates a new genus, Prorastomus, 
Artiodactyles, even at the base of the Eocene. 
tially Perissodactyle, p s some characters which point to a 
-chhadiateh Ungulate type from which the present orders have 
een evolved m these characters are the diminutive 
the mammalian foot have been derived. Of this family, only 
a single genus, Coryphodon (Bathmodon), is known, but there 
