3 io HISTORICAL PALEONTOLOGY. 



crowns, and are inserted in the jaw by two roots. Each 

 molar (fig. 228, A) looks as if it were composed of two 

 separate teeth united on the one side by their crowns; and it is 

 this peculiarity which is expressed by the generic name (Gr. 

 zeugle, a yoke; odous, tooth). The best-known species of 

 the genus is the Zeuglodon cetoides of Owen, which attained 

 a length of seventy feet. Remains of these gigantic Whales 

 are very common in the "Jackson Beds" of the Southern 

 United States. So common are they that, according to Dana, 



Fig. 228.Zeufflodon cetoides. A, Molar tooth of the natural iize ; B, Vertebra, 

 reduced in size. From the Middle Eocene of the United States. (After Lyell.) 



"the large vertebrae, some of them a foot and a half long and 

 a foot in diameter, were formerly so abundant over the 

 country, in Alabama, that they were used for making walls, or 

 were burned to rid the fields of them." 



The great and important order of the Hoofed Quadrupeds 

 (Ungulata) is represented in the Eocene by examples of both 

 of its two principal sections namely, those with an uneven 

 number of toes (one or three) on the foot {Perissodactyle Ungu- 

 lates), and those with an even number of toes (two or four) to 

 each foot (Artiodactyle Ungulates). Amongst the Odd-toed 

 Ungulates, the living family of the Tapirs (Tapirida) is repre- 

 sented by the genus Coryphodon of Owen. Nearly related to 

 the preceding are the species of Palaotherium, which have 

 a historical interest as being amongst the first of the Tertiary 

 Mammals investigated by the illustrious Cuvier. Several 

 species of Pal&othere are known, varying greatly in size, the 

 smallest being little bigger than a hare, whilst the largest must 

 have equalled a good-sized horse in its dimensions. The 

 species of Palceotherium appear to have agreed with the 



