86 Bulletin American Museum of Natural History. [Vol, XVI, 



dolichocephaly, which, it is important to note, is here accom- 

 panied by progressive lengthening of limb. 



In fact, dolichopody, in the broad sense of lengthening of 

 limb, is in general an adaptation to cursorial habits and 

 speed, associated with life on the plains, cropping front teeth, 

 absence of defensive weapons. 



The lengthening of the limb for the purpose of speed 

 appears in fact to have been the prime correlate of the lengthen- 

 ing of the skull. There are numerous cases where the elonga- 

 tion of the limbs and of the skull have developed pari passu, 

 notably in the case of the long-limbed Rhinoceroses as well 

 as in the Horses. It is also very characteristic of the long- 

 limbed Elotheres, which have extraordinarily long skulls, in 

 contrast with the remotely related Pigs. We reach the con- 

 clusion that both dolichocephaly and lengthening of neck, in 

 order to enable grazing animals to reach the ground, may be 

 primarily due to lengthening of limb. 



Exceptions to the Correlation of Dolichocephaly with 



Dolichopody and of Brachycephaly with 



Brachypody. 



There are, however, many exceptions to the correlation of 

 long limbs and long skulls. Among the races of men, although 

 there are notable cases of such correlation, there are also no- 

 table exceptions; the bipedal Primates generally offering an 

 exception to quadrupedal mammals. 



Again, the cursorial long-limbed Hyracodonts are a family 

 of Rhinoceroses with very long limbs and short skulls. Here, 

 however, brachycephaly is compensated for in a measure by 

 length of neck, possibly also by a substitution of browsing for 

 grazing habits. The most remarkable elongation of the 

 limbs and neck, in connection with an only moderately elon- 

 gate skull, is in the Giraffes, which are typical tree-browsers. 

 The opposite combination of long limbs with very long head 

 and short neck is exemplified in the Moose {Alces), habitually 

 a browser, which, like the giraffe, extends its mouth to the 

 ground with great difficulty. Whenever an animal acquires 



