VERTEBRATA: MAMMALIA. 659 



feeds upon insects, which it catches by protruding its long and 

 sticky tongue. 



As regards the distribution of the Monotremes in time, no 

 fossil remains referable to the order have ever been discovered, 

 with the exception of a gigantic Echidna, recorded by Mr 

 Krefft as occurring in the Post-tertiary deposits of Australia. 



ORDER II. MARSUPIALIA. The order Marsupialia con- 

 stitutes by itself the sub-class Didelphia, and forms with the 

 Monotremata the division of the Non-placental Mammals. 

 With the single exception of the genus Didelphys, which is 

 American, all the Marsupialia belong to the Melanesian pro- 

 vince ; that is to say, they all belong to Australia, Van Die- 

 men's Land, New Guinea, and some of the neighbouring 

 islands.* 



The following are the characters which distinguish the 

 order : 



Thesktdl is composed of distinct cranial bones united by sutures, 

 and they all possess true teeth ; whilst the angle of the lower jaw 

 is almost always inflected. 

 The pectoral arch has the 

 same form as in the higher 

 Mammals, and the coracoid 

 no longer reaches the anterior 

 end of the sternum. All pos- 

 sess the so-called " marsiipial 

 bones" or cartilages, attached 

 to the brim of the pelvis. The 



COrpUS CalloSUm is Very Small, Fig. 359. Lower jaw of the Wombat, viewed 



and has been asserted to be ab- angies^f the' jat. wing the str nsly infkcted 

 sent. The young Marsupials 



are born in a very imperfect condition, of very small size, and at a 

 stage when their development has proceeded to a very limited degree 

 only. (In the Kangaroo the period of gestation is only thirty- 

 nine days, and in the Didelphidce it is Only fifteen or seventeen 

 days.) There is no placenta or vascular communication between 

 the mother and foetus, parturition taking place before any neces- 

 sity arises for such an arrangement. As the young are born in 

 such an imperfect state of development, special arrangements are 

 required to secure their existence. When born, they are therefore, 

 in the great majority of cases, transferred by the mother to a 



* One Kangaroo (Macropus Bruijnii) is found in the Indian Archipelago, 

 along with five Phalangers, which differ from the Australian forms in hav- 

 ing the tail partially or entirely naked or scaly. There are also Tree- 

 kangaroos, and the curious Cuscus, distinguished by a prehensile tail, 

 large eyes, and slow progression. 



