CHAPTER XVI. 



PLACENTAL MAMMALS. 



55. The Placenta. In all the succeeding orders 

 of mammals the young are not born until their 

 internal organisation has become much more perfectly 

 developed than in the case of the young of the mar- 

 supials and monotremes ; and in order to provide for 

 their nutrition while they are thus growing, a peculiar 

 vascular organ, called the placenta, is developed, 

 whereby blood is supplied to the embryo for its 

 nourishment; hence they are called placental mam- 

 mals to distinguish them from the marsupials, which 

 are named non-placental mammals. 



Order 3, Edentata. The third mammalian order 

 is known as Edentata^ and includes the anteaters and 

 armadillos, which are easily recognised by the absence 

 of incisor teeth, at least in the middle of the jaws, so 

 that the front of the long, snout-like mouth appears 

 toothless, hence the name. They are all armed with 

 strong, usually sharp claws, and are clad with coarse 

 hair, or else with hard scales, and feed on insects, 

 small animals, or carrion. The true anteaters are 

 natives of South America, and are quite toothless (fig 

 34). They have exceedingly long, worm-like tongues, 

 which they can protrude for the purpose of entrap- 

 ping the insects whereon they feed ; and they have 

 an enormous pair of glands in the neck which secrete 

 a glutinous fluid to render the surface of the tongue 

 sticky. This long tongue they can retract rapidly, 



