1910.] Functions and Relations of the Molar Cusps. 191 



Hypoconulid, posterior to liypocone of corresponding 

 ii])})er molar. 

 II. Interlocking cusps. 



Upper molars: Protocone, fitting into talonid busin of corresponding 



lower molar. 

 Hypocone, fitting into trigonid basin of following lower 



molar. 

 Paracone (inner side), fitting into mid- valley of corre- 

 sponding lower molar. 

 Metacone (inner side), fitting into anterior valley of fol- 

 lowing lower molar (= interspace between talonid 

 of corresponding and trigonid of following molar). 

 Protoconule, fitting into inner valley between proto- 

 conid and hypoconid of corresponding lower molar. 

 Metaconule (inner face) fitting into valley between 

 talonid of corresponding and trigonid of succeeding 

 lower molars. 

 Lower molars: Protoconid, fitting into valley, or space between meta- 

 cone of preceding and paracone of corresponding 

 upper molars. 

 Hypoconid, fitting into mid-valley of trigon of corre- 

 sponding upper molar. 



Conclusions in regard to Trituberculy. 



From the "imperfect evidence at hand the following conclusions appear 

 to be indicated: 



(1) The multituberculate molar type is much older than the trituber- 

 cular type (}). 167). The supposed analogies with basin-shaped molars of 

 tritubercular derivation are not at all convincing, partly because none of 

 the alleged instances show much more than a verbal resemblance to the true 

 multituberculate type (p. 168). The multituberculate molar may conceiva- 

 bly be derived from a type more or less analogous with the Triconodont type. 



(2) While the Triconodonta may be related to the Trituberculata, 

 the assumed evidence of derivation of the tritubercular from a generalized 

 Triconodont molar seems invalid (p. 174), partly because Peralestes probably 

 has no near relationship with Spalacotherimn (p. 176). 



(3) The lower molars of Amphitherium are among the most generalized 

 tuberculo-sectorial types known (p. 179) and a detailed study of them afi'ords 

 grounds for inferring certain very primitive characters in the upper molars 

 (p. 180). 



