INTRODUCTION. 



IT. Sub-class. Implacentalia. 



Order XI. The Marsupialia or pouched mammals, 

 approaching to rodentia in the structure and 

 permanent separation of some of the bones of 

 their skulls ; having, in general, a more abun- 

 dant incisal dentition than placental mammals, 

 and always marsupial bones, performing impor- 

 tant functions in their vital economy. 



Order XII. The Monotremata, provided with mar- 

 supial bones, though destitute of pouch and 

 teeth; armed with spurs on the hinder feet, 

 and approaching towards the class reptilia in 

 many anatomical characters, constitute the 

 lowest, and, therefore, the last form in the 

 orders of mammalia. 



It would be easy to form a diagram, showing in 

 what manner these twelve orders are linked together 

 seriatim ; osculate among each other, or point to the 

 classes of vertebrata of different and lower organi- 

 sation ; but, in a volume of small dimensions, the 

 above general view will, we trust, be sufficient, and 

 as it is not intended to enter into the natural history 

 of man in this introduction, we shall merely state 

 that we do not admit more typical races than 

 Cuvier has pointed out ; all the other apparent 

 varieties being referable to intermixture of two or 

 even three, modified still more by climate, food, and 



