TERTIARY PERIOD. 515 



southwest. The abundance of Sharks' teeth is proof of the great 

 numbers of sharks in the waters, and also of the durability of their 

 teeth. The age was the time of culmination of the order of 

 Sharks. 



The Reptiles embrace species of Turtles and Crocodiles. 



The Mammals, in this age of Mammals, have a special interest. 

 No remains have yet been found in beds of the Claiborne epoch ; 

 but in the Jackson beds there are bones of one or more species of 

 Whale. The most common, called the Zeuglodon cetoides, was pro- 

 bably about seventy feet in length. The large vertebrae 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. 

 Some of the larger vertebrae are a foot and a half long and a foot 

 in diameter. Fig. 808 A shows one of the yo&e-shaped teeth to 

 which the name (from &vyhov, a yoke, and odovg, tooth) alludes. The 

 remains occur in Mississippi, Alabama, Georgia, and South Caro- 

 lina ; and a species of the genus is found in the Tertiary of Europe. 



The Titanotherium or White River beds of the Upper Missouri 

 are remarkable for the great variety of bones which they contain. 

 Remains of nearly forty species of extinct quadrupeds have been 

 already found, through the labors of Evans, Hayden, and other 

 explorers. According to the determinations of Leidy, they include 

 eight Carnivores, related somewhat to the Hyena, Bog, and Panther; 

 twenty-five Herbivores, among them two Rhinoceroses, and species 

 approaching the Tapir, Peccary, Deer, Camel, Horse; and four Ro- 

 dents, species of the Mouse tribe. 



The Titanothere [Titanotherium Proutii, fig. 816) is one of the Herbi- 

 vores, having some relations to the modern Tapir, but more like 

 the extinct Anoplothere and Palseothere of the European Tertiary. 

 One of the teeth is represented, half natural size, in fig. 816. The 

 animal was twice as large as a modern horse or the largest Paris 

 Palaeothere, and probably stood seven or eight feet high. Its re- 

 mains occur in the lowest bed of the series ; and hence, although so 

 gigantic in size, it was among the earliest species of the Tertiary 

 lake-region of the Upper Missouri. 



One of the Rhinoceroses (It. occidentalis Leidy) was about three- 

 fourths as large as the East India species, and another (JR. Nebras- 

 censis Leidy) half as large. Among the Ruminants there were 

 several species of a genus called Oreodon by Leidy, intermediate 

 between the Deer, Camel, and Hog. Fig. 818 represents a skull of 

 one of them. 



The Mammals of the Yorktown epoch from the beds of the At- 

 lantic coast, as far as known, are only species of Whales, Dolphins, 



