1898.] Osborn, Evolution of the Ainblypoda. Part I. 



181 



Suborder TALIGRADA Cope. 



Family Periptvchid^ Cope. 



Molars bunodont, primitive triangle 

 compressed in superior mokirs ; 

 secondary internal cusps developed 

 (protostyle and hypocone). Lower 

 molars with hypoconulid. Third 

 and fourth upper and lower premo- 

 lars enlarged. 



Family Pantolambdid.^' Cope. 



Molars selenodont, primitive triangle 

 less compressed. Lower molars 

 without hypoconulid. No second- 

 ary internal cusps. 



Family PERIPTYCHID^ Cope. 



In 1892 (op. cit., p. 47) Osborn pointed out that Prriptxcluis 

 is distinguished from the order Condylarthra (in which it had 

 been placed by Cope) first, because the tmsiis is not seiial, there 

 being a displacement of the astragalus upon the cuboid ; second, 



Fig 8. Pantolambda batktiiodon. Lateral view of skull, shewing wide e.vpusiire of mas- 

 toid. Coinpositiun of Nos. 2550 and 2549, Am. Mus. Coll. 



because it has the strictly tricronal molar of the Amblypoda. In 

 1897^ Cope adopted this view and removed the Periptychidce to 

 the Amblypoda. The close comparison of Pantolambda and 

 Periptvchus given below fully confirms this step. The condition 

 of the upper premolars as composed of two crescents and (unlike 



1 See Osborn and Earle, i8q2, p, 49. 



"^ Am. Nat., 1897, P- 335- Matthew has, however, retained the Periptychidae in the Condy- 

 larthra. 



