1883.] 323 [Cope. 



second the shorter and wider, as in the known species. The first molar 

 differs from that of both the latter, in having the tubercles of one side sepa- 

 rated nearly to the base. These tubercles are conic, and not flattened as 

 in G. foliatus and G. pollux, and the two rows are separated by a distinct 

 valley, as in the first named. There are five tubercles on one side, and four 

 on the other side of the crown, and in addition, two small cusps at the an- 

 terior extremity of each row, and another at the posterior extremity of one 

 of the rows. These additional cusplets are not present in the other species. 

 The last molar is relatively wider than in the other species. Its crown 

 is a good deal worn, but there are probably more than two rows of tuber- 

 cles, as there are some appendicular rows on one side of the crown at least. 



Measurements. M. 



Diameters M.ii antero P° sterior 0135 



*- transverse 0050 



Diameters M. ii \ anteroposterior 0090 



c transverse 0075 



The Upper Puerco ; D. Baldwin. 



General remarks on the characters op the Mammalia op the 



Puerco Epoch. 



I have already called attention to the fact that the Mammalia of the 

 Puerco epoch possess, with but few exceptions, superior molar teeth whose 

 crowns include only three of the component tubercles of the normal 

 mammalian molar, in a condition of full development.* In the number 

 of species of supposed placentals now known, sixty-seven, the proportion 

 of species (1), with quadrituberculate superior molars is even smaller, 

 being only four to sixty-three. The premolars display equally primitive 

 characters, and to these I wish now to draw attention. 



2. The presence of two internal tubercles of the fourth superior pre- 

 molar is unknown as yet in the fauna. 



3. The presence of two external cusps of the same tooth is known or 

 inferred in only five species in the sixty-seven, and in two of the five it is 

 of reduced size. 



4. The presence of one internal cusp of the fourth superior premolar is 

 demonstrated or inferred in all of the placental species. 



5. The presence of the internal cusp of the third superior premolar is, 

 on the other hand, only demonstrated in twenty -two species. In seven- 

 teen it is wanting. 



Referring to the inferior premolars : 



6. No species presents an internal cusp of the third premolar. 



7. An internal cusp of the fourth premolar is present in only fourteen 

 species. In twenty-nine species it is certainly wanting. 



* Proceedings of the American Philosophical Society, 1883, 562. American 

 Naturalist, 1883, 407. 



