OBJECTIONS AND DIFFICULTIES AND OTHER THEORIKs 



JIT 



Osborn (1904) presents New Palcvontological Difficulties in the 

 Prcmolar Analogy Theory. 



The crucial test of the premolar analogy theory is the hoinology of 

 the protocone of the superior molar. 



If the protocone is the antero-external cusp in the upper pre- 

 molars and the antero-internal cusp in the upper molars, the premolar 

 analogy theory falls to the ground, and the Cope-Osborn theory remains 

 thoroughly substantiated. From Osborn's latest contribution (1904) to 

 the tritubercular theory 1 we make the following abstract : 



In addition to the evidence afforded by the upper teeth of Tri- 

 conodon, in which the main cone is central, and that seen in the upper 



External or -maxillary 



/ 



i.of. 



A 



Painted cr internal view , 



Fio. 20ii. Superior molars of Dryolextes Marsh. Upper Jurassic, Wyoming. A. Series of the 

 ; side external and crown views. B. Series of the right side, external, crown and internal 



i. o. f. infraorbital foramen. Other 



left 



views. Yale Museum, c, c, c, external and internal cingula. 



abbreviations as in Fig. 12. (Cf. Fig. '207 (2) and p. 220.) 



teeth of Peralestes (in the British Museum), in which the main cone is 

 internal (Fig. 12), and the upper teeth of Kurtodon (British Museum), in 

 which the main cone is internal (Fig. 13), the original theory was sup- 

 ported by Professor Marsh's statement that in the upper molars of 

 Dnjolcstcs (Yale Museum) the main cone was internal ; in each case 

 the main cone is believed to be the protocone or reptilian cone. 



The two specimens here referred to in the Yale Museum exhibit 

 perfectly the structure of both crowns and fangs, of seven superior 

 molar teeth, bringing out the following important points (Fig. 206): 



(1) The molars are sharply distinguished from the premolars, which 

 are bifanged teeth with simple, laterally compressed crowns. 



Osborn, H. F., " Palteontological Evidence for the Original Tritubercular Theory.'" 

 Amer. Jour. &/., Vol. XVII., Apr. 1904. pp. 321-3-23. 



