MARSUPIALIA. 557 



Echidna hystrix is the best-known species, and in some exter- 

 nal respects is not unlike a large hedgehog, having the back 

 covered with strong spines, interspersed with a general coating 

 of bristly hairs. The snout has not the form of a duck's bill, 

 as in the Ornithorhynchus, but the two mandibles are greatly 

 elongated, and are enclosed in a continuous skin till close 

 upon their extremities, where there is a small aperture for the 

 protrusion of a very long and flexible tongue. The jaws are 

 wholly devoid of teeth or anything in the place of teeth ; and 

 the nostrils are placed at the extremity of the cylindrical snout. 

 The feet have five toes each, furnished with strong curved 

 digging-claws, but the toes are not webbed. The Echidna 

 measures from fifteen to eighteen inches in length, and is a 

 nocturnal animal. It lives in burrows, and feeds upon insects, 

 which it catches by protruding its long and sticky tongue. 



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- 

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

 islands.* 



The following are the characters which distinguish the 

 order : 



The skull 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 cora- 

 coid no longer reaches the anterior end of the sternum. All 

 possess the so-called " marsupial bones," attached to the brim 

 of the pelvis. The corpus callosum is very small, and has 

 been asserted to be absent. 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 about thirty-nine days, and in the Didelphidce, it is said to 

 be only fifteen or seventeen days.) It is believed that there 

 is no placenta or vascular communication between the mother 

 and foetus, parturition taking place before any necessity arises 



* One Kangaroo (Macropus JBruynii) 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. 



