OBJECTIONS AND DIFFICULTIES AND OTHER THEORIES 



UlM 



derived from the Atlantosaurus-beds mammals entirely supports the 

 evidence of embryology and agrees in general with the ' pre-molar 



000 



a 



ooo 



3 



E 4 



Fio. 208. [Gidley's] Suggested Plujletic History of Two Types or Complex: Molars. [As in 

 Osborn's diagram [see Fig. 41, p. 61], the solid black dots represent the cusps of the upper 

 molars, the circles, those of the lower molars.] 1 to 6, Phyletic history of the "Trituber- 

 cular " type ; a to d, Phyletic history of the " Triconodont " type ; < , /, From the brachyodont 

 Triconodont stage to the bilobed hypsodont type of molar. 



A, B, C, E, and G compare witli A, B, /', K, and G in Osborn's diagram [see Fig. 41, p. 01] ; 

 4, Dryolestes type, Atlantosaurus beds ('? Upper Jurassic) ; 5 and 0, Protolambda or Pediomvs type, 

 Laramie beds (Upper Cretaceous); d, Tricododon type, Atlantosaurus beds (? Upper Jurassic); 

 /, Palwolagus type, White River beds (Oligocene). From Gidley. 



analogy ' theory. Thus, the evidence from all sources points over- 

 whelmingly to the conclusion that the primary cone is to be found 

 on the outer side in the upper molars of primitive trituberculate forms 



