29 



and Pacific Coast. The best known genus is Priscodelphinns^ of 

 which several species have been described. Several other 

 generic names which have been applied to fragments need not 

 here be enumerated. Tn none of the Tertiary species of this 

 family were the cervical vertebras ankylosed. The S])erm 

 Whales {Catodontkkfi) were also abundant throughout the Ter- 

 tiary, and with them in the earlier beds, various Ziphioid forms 

 have been found. The toothless Balwnidce 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 

 Old World, occur in the Miocene of our Eastern Coast, and 

 throughout the later Tertiary. The specimens described have 

 all been referred to the genus Manaius, and seem closely 

 related to our living species. In the Tertiary of Jamaica, a 

 skull has been found which indicates a new genus, Prorastoraus^ 

 also allied to the existing Manatee. The genus Rhylina^ once 

 abundant on our Northwest Coast, has recently become extinct. 



The Ungulates are the most abundant Mammals in the Ter- 

 tiary, and the most important; since they include a great 

 variety of tj^pes, some of which we can trace through their 

 various changes down to the modified forms that represent 

 them to-day. Of the various divisions in this comprehensive 

 group, the Perissodactyle, or odd-toed Ungulates, are evidently 

 the oldest, and throughout the Eocene are the prevailing forms. 

 Although all of the Perissodactyles of the earlier Tertiary are 

 more or less generalized, they are still quite distinct from the 

 Artiodactyles, even at the base of the Eocene. One 

 family, however, the Coryphodonlidce, which is well represented 

 at this horizon, both in America and Europe, although essen- 

 tially Perissodactyle, possesses some characters which point to a 

 primitive Ungulate type from which the present orders have 

 been evolved. Among these characters are the diminutive 

 brain, which in size and form approaches that of the Reptiles, 

 and also the five-toed feet from which all the various forms of 

 the mammalian foot have been derived. Of this family, only 



