72 INTRODUCTION. 



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

 sors ; the true Quadrumana never having 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 numher of incisors. 



All the Marsupial animals appear to have four 

 true molars (if we except the two edentate species, 

 Echidna and Ornithorhynchus,} whereas, in the Pla- 

 cental series the normal numher 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 Marsupiata, and those of 

 other orders of Mammalia, already pointed out, the 

 skall 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 Thylacinus near the Dogs, 

 the Opossums in the Insectivora or Quadrumana, &c. should 

 not have omitted to notice the important difference, observable 

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

 mals in question. 



j- In this, and many other characters, the Rodentia appear 

 to approach most nearly to the Marsupiata. 



