OF EVOLUTION. 



77 



sacral vertebrae ! In relative size this diminutive 

 brain, which is proportionately the smallest brain 

 known among mammals, whether recent or fos- 

 sil, is surpassed by the brains of many reptiles. 

 Hoplophoneus oreodontis, one of the sabre- 

 toothed cats, although of about the size of a 

 panther, had a brain no larger than that of the 

 domestic cat. The peculiar sulci or gyri seen 



3, Skull of Limnohyus robustus (tapiroid), Middle Eocene ; 4, Amynodon 

 advenus (rhinoceros), Upper Eocene. (After Marsh.) 



