72 INTRODUCTION. 



sent an increase of ten in tlie total number of inci- 

 sors ; the true Quadrumana never liaving more than 

 four in each jaw. The Thylacinus and Dasyures 

 differ from the corresponding Carnivorous Mammals, 

 in the Placental series also^ in having an increase in 

 the number of incisors. 



All the Marsu2)ial animals appear to have four 

 true molars (if we except the two edentate species. 

 Echidna and OrnitJwrhynchus,) whereas, in the Pla- 

 cental series the normal number appears to be three. 

 If we compare the Thylacinus with the Dogs, we not 

 only find a remarkable difference in the form of the 

 true molars, these most nearly resembling the car- 

 nassiers of the ordinary carnivora, but we find an 

 increase of 8 in the number.* 



In addition to the points of distinction between 

 the species of the order Marsujoiata, and those of 

 other orders of Mammalia, already pointed out, the 

 skull furnishes some very important characters. 



One of the most remarkable features in the skull 

 of the Marsupial animal, consists in the permanent 

 separation of the greater portion of the bones — they 

 do not anchylose in the adult and old individuals, as 

 do most of the bones of the skull in the Placental 

 series :t the temporal bone generally presents a per- 



* The advocates for placing the Thjlachius near the Dogs, 

 the Opossums in the Insectivora or Quadrumana^ ike. should 

 not have omitted to notice the important difference, observable 

 in the teeth and other points of dissimilarity between the ani- 

 mals in question. 



i* In this, and many other characters, the Rodentia appear 

 to approach most nearly to the Marsupiata. 



