VERTEBRATA. 273 



Order 8. Sirenia (seiren, a siren, or Mermaid) are like 

 the Cetacea in shape, but are herbivorous, and frequent 

 great rivers and estuaries. They have both a temporary 

 and permanent set of teeth, a narrow brain, and nostrils 

 on the top of a large snout. The Dugong and Manatee 

 are illustrations of this order. 



Order 9. Proboscidia include the Elephant, the extinct 

 Mastodon, the Dinothere, and the Mammoth. There 

 are no canine teeth, but the incisors are prolonged into 

 tusks, which in the Elephant grow from the upper jaw, 

 in the Dinothere from the lower jaw, and in the Masto- 

 don from both jaws. The nose is prolonged into a long, 

 flexible, sensitive trunk, which is terminated by a small 

 prehensile appendage like a finger. Cuvier counted 

 20,000 distinct muscles in an Elephant's trunk. The 

 limbs are massive, each with five toes incased in hoofs, 

 and with a thick pad intervening between the toes and 

 the ground. 



Order 10. Ungulata, or Hoofed Quadrupeds, have 

 four well-developed limbs, each having not more than 

 four complete toes, and each toe being incased in a hoof. 

 The leg is therefore for support and motion, and not for 

 prehension. They have temporary and permanent sets 

 of teeth. The Odd-toed Ungulates include the Horse, 

 the Rhinoceros, and the Tapir. The Horse, which 

 with the Ass and Zebra, made up the old order of Soli- 

 dungula, has only a single perfect toe on each foot, 

 coated with a nail, called a hoof, so that the horse walks 

 and runs not merely on its toes, but on its nails. The 

 Rhinoceros has three toes on each foot, and carries one 

 or two horns on the skin of the nose. 



