68 MAMMALIAN DESCENT. [Lect. III. 



process) is a mere spur, as in the Eutheria generally. 

 So also tlie vertebrae, the ribs, and the sternum ; 

 these are quite normal, having taken on the characters 

 we are familiar with in the hio-her kinds. 



The limbs are very instructive. The front pair are 

 very similar to what we find in Insectivora and Eodents, 

 and are not much modified, but the hind pair are very 

 much specialised in those that can take long leaps — as 

 the Kangaroos. The Opossums of America, and the 

 Phalangers of Australia, have the hallux (great toe) 

 short and opposable, as in the Dormouse, and in the 

 Quadrumana (Apes and Monkeys), generally. From such 

 a foot as that there is every transitional form to that of 

 the Kangaroo, where the hallux or first toe is gone, 

 the second and third extremely long and delicate and 

 evidently useless, whilst the fourth is very large, and 

 the fifth moderate. 



One peculiarity of these pouched animals is seen in 

 their dentition. Several years ago. Professor Flower 

 showed that only the third false grinder (pre-molar) has 

 a predecessor. This milk tooth is like a true molar ; the 

 tooth jiattern is simple, quite unlike that of the high 

 Herbivora. The Rodents, which are lower, are extremely 

 variable in this respect, and the dentition, in some of them, 

 assumes a high condition, with extreme specialisation. 



As the metropolis of a country is the most instructive 

 as well as the most important of its towns, so the skull 

 takes to itself that which is best and noblest in the 



