its enemies by flight. These powers, as is well known, are secured 

 to the herbivorous species of the placental Mammalia, by an ungu- 

 late structure of four pretty equally developed members. Such a 

 structure, however, would have been incompatible with the pro- 

 creative ceconomy of the Kangaroo. It is therefore organized for 

 rapid locomotion by an excessive development of the hinder extre- 

 mities ; and these alone serve as the instruments of flight, which is 

 performed by a succession of extensive bounds. The tail also is 

 of great power and length, and in the stationary position, the body 

 is supported erect on the tripod formed by the tail and hind legs ; 

 while in easy progression the tail serves as a crutch upon which 

 and the fore feet the body is sustained while the hind legs are swung 

 forwards. 



" As the Australasian continent, the great metropolis of the Mar- 

 supial quadrupeds, still remains but very partially explored ; and as 

 new species and even genera of Marsupials continue at each expe- 

 dition to reward the reseaxxhes of the scientific traveller; and as 

 moreover the recoveiy of two lost but distinct genera from the ruins 

 of a former world makes it reasonable to suppose that other types 

 of Marsupials remain still hidden in the crust of the earth ; it can 

 hardly be expected that the zoologist should be able to arrange in 

 a nat\iral series, with easy transitions according to the order of their 

 affinities, the few and diversified forms of this implacental subclass 

 which are at present known. The greatest num1)er of correspond- 

 encies, as it appears to me, will be expressed by taking the modi- 

 fications of the digestive system as the guide to the formation of 

 the primary groups of the MarsupiaI'm. 



" The continent, however, in which the Marsupials ' most do con- 

 gregate ' is characterized by the paucity of organized matter upon 

 its surface, and few of them, consequently, are nourished by a very 

 well-defined diet. No large carnivorous quadruped could in fact 

 have existed in the wilds of Australia prior to the introduction of 

 civilized man and his attendant herds : and we find, in fact, that 

 the native genera which are the most decidedly carnivorous, do not 

 include species larger than the dog : we can only reckon among 

 these strictly carnivorous species the Thylacines and the Dasyures ; 

 and, on the other hand, not more than two or three Marsupial 

 genera feed exclusively on vegetable substances. The rest of them 

 derive a promiscuous nutriment from dead or decayed animal and 

 vegetable matter, Crustacea, and the refuse of the sea-shore, insects 

 in their perfect and larva states, live birds, young and succulent 

 sprouts, leaves, fruits, &c. The terms, therefore, which will be 

 given to the diff'erent primary subdivisions in the present classifica- 

 tion of the Marsupialia must not be understood to indicate strictly 

 or exclusively the nature of the food of the species severally in- 

 cluded in these groups, but rather their general tendenc}^ to select 

 for their support the substances implied by those designations." 



Tribe I. SARCOPHAGA. 

 The genera in this tribe are the most decidedly carnivorous of all 



