8o Bulletin American Museum of Natural History. [Vol. XVI, 



dolichocephaly and brachycephaly, and finally some of the 

 facts which await explanation. 



In applying these terms to the lower mammals we refer to 

 the skull as a whole, whereas in man the reference is only to 

 the cranium. 



The Long and the Broad Skull. 



The three skulls photographed below from the American 

 Museum collection (Fig. 2) are three nearly contemporary 

 species of Eocene Titanotheres which illustrate admirably 

 dolichocephaly, brachycephaly, and the neutral or inter- 



A B C 



Fig. 2. Eocene Titanotheres. ,-i, Brachycephalic, Palaosyops paludosus. 5, Mesati- 

 cephalic, Linmohyops mauteoceras. C, Dolichocephalic, Telmaiotherimii cormdum. 



mediate condition of mesaticephaly. The species are the 

 classic PalcBosyops paludosus, the extremely long and nar- 

 row Telmatothermm cornutum, and the moderately broad 

 Limnohyops manteoceras . The first and second species are 

 believed to belong to side lines which became extinct; the 

 third, more generalized, form is now believed to have given 

 origin to the Oligocene Titanotheres, although this inference 



