6 THE AMERICAN MUSEUM JOURNAL 



fall into one or another of the living families and are more or 

 less directly ancestral to the modern beasts of prey. The re- 

 mainder belong to several extinct branches, not ancestral to any 

 of the modern families, and are combined in the rather hetero- 

 geneous group of Creodonta. Seals and Walruses have not been 

 found fossil, except in the most recent deposits, and nothing is 

 known of their evolution. 



A. CREODONTA, OR PRIMITIVE CARNIVORA. 



In all modern Carnivora one tooth in the upper and one in 

 the lower jaw are enlarged and especially adapted to the cutting 

 of flesh. Each consists mainly of a high strong crest, or ridge. 



FIG. 2. UPPER AND LOWER TEETH OF THE WOLF 

 Shows the carnassials or flesh-cutting teeth (the fourth premolar in the upper jaw, the first true molar 



in the lower) 



and the two crests, or "blades," work against each other like the 

 blades of a pair of scissors. These teeth are called the "car- 

 nassials," or flesh-teeth. In all the modem Carnivora the fourth 

 (last) upper premolar and the first lower true molar are the car- 

 nassial teeth. The fossil species show the gradual evolution of 

 this specialized tooth in the various families of Carnivores. In 

 the Creodonta, on the other hand, there is either no carnassial 

 tooth, or it is developed from other teeth of the series, — in one 

 group the first upper and second lower true molars, in another 

 the second upper and third lower molars. (Compare Figures 2, 

 3, 4 and 5.) 



