LESSONS IN ZOOLOGY. 307 



folded brain; both have marsupial bones, but only the echidna 

 has a pouch, and both live on insects. 



The Marsupialia. This order includes the kangaroo, wombat, 

 bandicoot and others of Australia, and the opossum of the 

 United States. The females of this order are furnished with an 

 abdominal pouch or marsupium, for the immature young after 

 birth. The marsupials form no placenta, so that the young 

 are born early in their embryonic life and transferred to the 

 pouch, where they attach themselves to the nipples of the mam- 

 mary gland and remain there during the remainder of their 

 helpless existence. Some of this order are carnivorous, some 

 herbivorous and others are omnivorous; some are specially 

 adapted for jumping, others for climbing, and others have a 

 naked prehensile tail; so that they are quite varied in form and 

 habits. 



The Edentata. The members of this order are all sluggish, 

 stupid animals, with a small smooth brain; the teeth are fre- 

 quently absent, and when present are usually incomplete or im- 

 mature. To this group belong the ant-eaters, armadillos and 

 sloths. The ant-eaters have an elongated narrow snout, protru- 

 sible tongue and weak jaws; the legs are short and adapted for 

 digging. They live mainly on ants and termites. The armadil- 

 los are covered with bony plates, having legs and claws fitted for 

 digging. They can rapidly bury themselves in the ground when 

 pursued, and most of them can roll themselves into a ball that 

 is well protected by bony plates from the attacks of enemies. 

 The sloths are strictly arboreal, hanging by their curved claws 

 from the underside of branches. The sloth, armadillo and one 

 ant-eater live in South America, while the scaly ant-eater is 

 found in Asia and Africa. The remains of many gigantic edent- 

 ates are found in the later rocks of South America. 



The Cetacea. The members of this order are aquatic mam- 

 malia, with fin-like anterior and no posterior extremities. The 

 body is fish-like in form, only that the caudal fin is horizontal, 

 not vertical as in the fishes. The surface is usually devoid of hair, 

 but a thick subcutaneous layer of fat serves to protect from cold, 



