300 HISTORICAL PALEONTOLOGY. 



which the teeth differed from those of all existing forms in 

 being of two kinds, — the front ones being conical incisors, 

 whilst the back teeth or molars have serrated triangular 

 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 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 Zeuglodo?i 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, 

 " 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 

 ot 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 [Tapiridce) is repre- 

 sented by the genus Coryphodon of Owen. Nearly related to 

 the preceding are the species of PalcBotherium, which have 

 a historical interest as being amongst the first of the Tertiary 

 Mammals investigated by the illustrious Cuvier. Several 

 species of PalcEothere 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 

 existing Tapirs in possessing a lengthened and flexible nose, 

 which formed a short proboscis or trunk (fig. 229), suitable as 

 an instrument for stripping off the foHage of trees — the char- 

 acters of the molar teeth showing them to have been strictly 

 herbivorous in their habits. They differ, however, from the 

 Tapirs, amongst other characters, in the fact that both the 

 fore and the hind feet possessed three toes each ; whereas in 

 the latter there are four toes on each fore-foot, and the hind- 

 feet alone are three-toed. The remains of PalcBotheria have 

 been found in such abundance in certain localities as to show 

 that these animals roamed in great herds over the fertile plains 

 of France and the south of England during the later portion 

 of the Eocene period. The accompanying illustration (fig. 

 229) represents the notion which the great Cuvier was induced 



