192 



Bulletin American Museum of Natural History, [^'ol. XX^'II, 



Fig. 13. Internal view of tlie cheek teeth (riglit side) in various mammals, showing that 

 the protocone fits into the valley of the talonid of the corresponding lower molar, while the 

 hypocone fits into the valley of the trigonid of the next succeeding lower molar. The para- 

 and metaconid fit into the space between the upper teeth. No. 1. Centetes. No. 2, Didelpfiis, 

 No. 3, Erinaceus, No. 4, Telmatherium cultrideus, an Eocene Titanothere. Prepared under the 

 writer's direction for Professor Osborn's 'Evolution of the Mammalian Molar Teeth.' 



p.= protocone, /).= hypocone, w.= metaconid, t.= talonid. 



