120 VERTEBRATA. MAMMALIA. 



class, parallel with, but distinct from, the ordinary 

 Mammalia. A more intimate knowledge of their ana- 

 tomical structure, the result of much attention and 

 study, has convinced most modern zoologists of the 

 propriety of this separation ; and the class or sub-class 

 MARSUPIALIA, divided into its own orders, and in- 

 cluding the Echidna and Ornithorhynchus, is now ge- 

 nerally considered as intermediate between the vivi- 

 parous and oviparous VERTEBRATA, leading, however, 

 to the Reptiles, rather than to the Birds. For con- 

 venience' sake, however, we shall in a work like the 

 present adhere to the arrangement of Cuvier. 



We find in these animals great variety of struc- 

 ture, dentition, digestion, prehension, progression, 

 food, &c., affording us parallels to the Carnivora, 

 Insectivora, Herbivora, and Rodentia. The great 

 peculiarity by which they are associated, is the pre- 

 mature birth of the young, which, when produced, 

 is compared by Professor Owen (in the case of the 

 great Kangaroo Macropus Major) to an earth worm, 

 in the colour and semi-transparency of the skin. 

 The pouch into which it is transferred for protec- 

 tion, is formed by a doubling of the skin of the abdo- 

 men, the orifice of which is capable of being firmly 

 closed. At this period it is perfectly helpless, though 

 it can move its limbs. It remains in the pouch an 

 indefinite time, several months at least, until it has 

 attained a large size ; and, even long after its ex- 

 clusion, it occasionally returns into the maternal 

 pouch for protection. The other points which mark 

 the distinctness of this class of animals are found in 



