1902.] Osbor7t,Dolichocephaly and Brachycephaly in Mammals, '^'^y 



BRACK YCEPHALY. DOLICHOCEPHALY. 



Skull. 



Tympanic bulla Thrust inward Exposed laterally. 



Foramen ovale and f . 



lacerum medius. . . Approximated Separated by a bridge 



of bone. 



Foramen lacerum 

 medius and f. lac- 

 erum posterius. . . . Approximated Separated by periotic. 



Alisphenoid canal.. . Abbreviated Elongate. 



Presphenoid Abbreviated Elongate. 



Vomer Thrust backward .... 



Premaxillary sym- 

 physis Abbreviated Elongate. 



Horns Transversely expand- 

 ed Not so expanded. 



Jaw. 



Jaw Shortened, thick- Elongate, with straight 



ened, deepened. lower border and 



backwardly pro- 

 duced angle. 

 Area of insertion for 



temiporal muscle. . Reduced Balance maintained. 



Coronoid process. . . . Reduced Lengthened antero- 



posteriorly. 

 Mandibular symphy- 

 sis Abbreviated Elongate. 



The above characters are chiefly observed in the Titan- 

 otheres, in which the most careful comparison of dolicho- 

 cephalic and brachy cephalic skulls has been made. 



Many characters in the first column apply with equal force 

 to the Primates which are progressively brachy cephalic, 

 marking the passage from the more dolichocephalic Lemurs 

 and Baboons to the more brachycephalic Lemurs, Monkeys, 

 and Apes. 



On the other hand manv characters in the second column 

 apply also among the Horses, which are progressively dolicho- 

 cephalic. 



Many of these characters also distinguish the brachy- 

 cephalic from the dolichocephalic Rhinoceroses. 



There are, however, notable exceptions, as shown below. 



