210 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



primitive types of the order of the Rhynchoce- 

 phalians. The marine Mammals of the family of 

 the Whales show a specialization of their anterior 

 limb, which does not lack similarity to that of 

 the Ichthyosaurs, notwithstanding that the number 

 of digits remain at the normal figure of five. 



The transformation of the anterior limb of the 

 Vertebrates into an organ of flight would show us in 

 the same way a specialization by atrophy of the hand 

 in the Birds, and, on the contrary, by an exagger- 

 ated development and multiplication of the phalanges 

 of the fifth finger, in the Flying Reptiles or Ptero- 

 saurians of Secondary times. 



Another mode of specialization common to a 

 great number of phyletic branches consists in the 

 production of offensive or defensive weapons car- 

 ried to the most remarkable perfection. Into this 

 order of ideas there enters the differentiation, 

 among Carnivora, of the canine teeth into sharp 

 daggers with edges sometimes sharp and sometimes 

 saw-like. The most different groups, the Stegoce- 

 phala, the Theromorphs, the Dinosaurs, and the 

 Mammals, all offer examples of this differentiation 

 of the canine. We can point as extreme degrees of 

 specialization to the formidable tooth, shaped like a. 

 curved sword blade, of the Jurassic Megalosaurus and 

 to the terrible canine tooth possessed by the great 

 felines of the extinct branch Machairodus,* towards 

 the end of the Tertiary and up to Quaternary times. 

 Other still more specialized dental forms are the 

 tusks which attain in the Proboscidian group 

 their maximum power. In the Mastodon arvernensis, 



* The sabre-toothed tiger. ED. 



