1902.] Osborn, Dolichocephaly and Brachycephaly in Mammals. 87 



the shrub- or tree-browsing habit, therefore, as in the case of 

 Rhinoceros bicoriiis, a new factor is introduced. Other fam- 

 ihes in which the browsing habit appears to have been ac- 

 quired secondarily are the ChaUcotheriidffi, Agriochoeridae, and 

 Anoplotheriidae. 



Again, among the Carnivora the Dogs are typically long- 

 skulled and long-limbed or cursorial animals. A dog feeds 

 in a standing position, the food held upon the ground b}^ the 

 fore feet, the limbs being somewhat flexed. In this family 

 the skull and limb correlation seems to hold good. Moreover, 

 the short-faced dogs are generally short limbed. Cats, on the 

 other hand, present a decided exception, because they are 

 brachycephalic and dolichopodal, the Cheetah, for example, 

 having an exceptionally short skull and elongate limbs. We 

 should recall, however, that cats always feed in the recum- 

 bent or semirecumbent position, crouching or lying down. 

 Thus the abbreviation of the Cat skull is correlated with the 

 functions of the teeth and not with those of the limbs, be- 

 cause the Cats have a special position in feeding. Similarly 

 the Proboscidea are extremely brachycephalic and long- 

 limbed, but the exceptional elongation of the limbs is com- 

 pensated for by the development of a proboscis. 



To sum up, the numerous exceptions to the correlation of 

 skull and limb proportions are mostly capable of special 

 adaptive explanations, and, as we shall see below, when cor- 

 relation does occur it is probably adaptive also. In brief, 

 there is no innate, invari- 

 able law of correlation; 

 skull and limbs may or 

 may not be dependent 

 upon each other. 



But when such correla- 

 tion does occur, as in Tel- 

 matotherium or Hyopotaniiis 



on the one hand, or in Tele- Fig. 5. Brachycephalic skull of Monkey, 



. . Jilaccacus sp., juv. 



oceras on the other, it is 



likely to affect the whole skeleton : length of the cervical 



and dorsal vertebrae, form of the scapula and ilium, length 



