MACROPODIDjE. 169 



I have thought it desirable to enter into these 

 particulars as regards the number of the teeth in the 

 Kangaroos, since M. F. Cuvier has founded two 

 genera upon the difference in the number of the 

 molars in certain species, to those which have only 

 four molars, and in which the tip of the muzzle is 

 covered with hair, (having only a narrow naked 

 space around the nostrils) he restricts the generic 

 title Macropus, and places in this genus the M. 

 giganteus M.fuliginosus, M. ruficollis } and M. rufo- 

 griseus. Those species which have the tip of the 

 muzzle naked, the tail sparingly clothed with hair,* 

 and four true molars and one false molar on either 

 side of each jaw, are thrown together by the same 

 author under the generic title Halmaturus, a name 

 which had originally been applied by Illiger, to all 



To assist the beginner in the study of Mammalia, I may 

 mention that, as a general rule, the false molars of both jaws are 

 furnished with one, or most commonly, two roots, the hinder- 

 most false molar (or that which in the Car?iivora is termed the 

 carnassie.r,) in the upper jaw, has three roots, and so have the 

 true molars of the upper jaw ; but in the under jaw the 

 carnassier and true molars have but two roots. 



My attention was first drawn to the fact that there exists a 

 difference between the Marsupiata and the Placental Mam- 

 malia as regards the number of true molars, upon comparing 

 the skull of the Thylacinus with that of the Dog and allied 

 animals, and I believe at that time no such difference had 

 been pointed out. 



* This character is certainly not connected with the other 

 peculiarities mentioned ; on the contrary, it is in the group 

 with the naked muzzle and five molars, that we find the tail 

 often much more densely clothed than in M. F. Cuvier 's 

 genus, Masropus. 



