/ 



TALIGRADA. 603 



material to deinonstrate whether this genus belongs to the Amhlypoda or 

 Perissodactyla.'''' 



From what has preceded it is quite evident that the ensemble of 

 characters is predominantly that of the former order. 



It is now apparent that the type of superior molar tooth which pre- 

 dominated during the Puerco epoch was triangular; that is, with two ex- 

 ternal and one internal tubercles. Thus of forty-one species of Mammalia 

 of which the superior molars are known, all but four have three tubercles 

 of the crown, and in this thirty-eight triangular ones we may include those 

 of three species of Periptychus, which have a small supplementary lobe on 

 each side of the median principal inner tubercle. 



This fact is important as indicating the mode of development of tlie 

 various types of superior molar teeth, on which we have not heretofore had 

 clear light. In the first place, this type of molar exists to-day only in the 

 insectivorous and carnivorous Marsupialia; in the Insectivora, and the 

 tubercular molars of such Carnivora as possess them (excepting the planti- 

 grades). In the Ungulates the principal traces of it are to be found in the 

 molars of the Coryphodontidce of the Wasatch, and Dinocerafa of the Bridger 

 Eocenes. In later epochs it is chiefly seen only in the last superior molar. 



It is also evident that the quadritubercular molar is derived from the 

 tritubercular by the addition of a lobe of the inner part of a cingulum of the 

 posterior base of the crown. Transitional states are seen in some of the 

 Periptychidce (Anisonchus) and in the sectorials of the Procyonidce. 



Pantolambda bathmodon Cope. 



American Naturalist, 18b2, p. 418. 

 Plate XXIX d. 



The bases of the inferior Pni. iii and iv are subquadrate, the inner side 

 rounded, that of the iv relatively the wider. On the iii the median keel 

 constitutes the heel ; on the iv, the keel is in the center of a wide heel. No 

 cingula. The first true molar has an anterior cingulum, but no external 

 one. The enamel is wrinkled where not worn. Diameters of Pm. iii, an- 

 teroposterior, .009 ; transverse, .007 ; of Pm. iv, anteroposterior, .009; trans- 



