Cope.] 326 [Dec. 7 . 



In a former article, "On the Homologies of the Molar Teeth," etc., I 

 traced the modifications of the superior and many of the inferior molars ot 

 the ungulate mammals to a parent quadrituberculate type. In a subse- 

 quent essay* I traced the origin of the inferior sectorial to a primitive five- 

 tubercled, or " tubercular sectorial" type. Farther than this I did not go, 

 and made no attempt to derive the few cases of triangular superior molars 

 then known, nor the type of the superior sectorial. The revelations of the 

 Puerco fauna show, that the superior molars of both ungulate and ungui- 

 culate mammalia have been derived from a tritubercular type ; and that 

 the inferior true molars of both have been derived from a "tubercular 

 sectorial " type. Shall we look for the origin of the latter in a trituber- 

 cular tooth also, i. e. tubercular sectorial without heel ; and will the 

 crowns of the true molars of the primitive mammals alternate with, in- 

 stead of oppose each other? This is a probable result of future discovery. 



* Journal Academy Natural Sciences, Philadelphia, March, 1875. 



Published January 2, 1884. 



