172 T7XGTJLATA. 



Suborder CONDYLARTHRA. 



The primitive mammals forming this Suborder are grouped 

 by Cope * with the Hyracoidea and perhaps the Toxodontia in a 

 division termed Taxeopoda, which is characterized by the scaphoid 

 of the carpus being supported by the trapezoid and not by the 

 magnum, the latter supporting the lunar ; in the tarsus the cuboid 

 articulates proximally with the calcaneum only. The component 

 bones of both the carpus and tarsus mutually interlock only to a very 

 slight extent ; and the whole structure of these parts is the simplest 

 type obtaining in the Ungulata. The present Suborder is charac- 

 terized by a bunodont or (in the higher forms) a lophodont type of 

 cheek-dentition, the characters of which foreshadow those of both the 

 Artiodactyla and Perissodactyla : there are usually five digits to both 

 the pes and manus, the terminal phalangeals being acuminate ; the 

 humerus has an ectepicondylar foramen, the astragalus a uniformly 

 convex distal articular surface, the femur a third trochanter, and there 

 are no fibular facettes on either the astragalus or the calcaneum. The 

 skeleton of the type genus of the family Plienacodontidce is figured 

 in the accompanying woodcut (fig. 23) ; and apparently indicates a 

 primitive form allied to Hyracotherium. 



Family PEKIPTYCHID^E. 



The dentition is bunodont ; the digits five on each foot ; the 

 astragalus has no trochlea ; and the premolars are simple. 



Genus PERIPTYCHUS, Cope 2 . 

 Syn. Catathlceus, Cope 3 . 



Dentition : — I. ^y^, C. \, Pm. |, M. |. The upper true molars 

 have external accessory cusps, but these are not present in the lower 

 true molars. The lower canines are of small size and the incisors 

 small 4 . 



1 Proc. Amer. Phil. Soc. vol. xx. p. 444 (1882), and Amer. Nat. toI. xviii. 

 pp. 791-805 (1884). See also Sehlosser, Zool. Anzeig., No. 210 (1885). 



2 Amer. Nat, vol. xv. p. 337 (1881). 



3 Ibid. vol. xv. p. 829 (1881). 



4 The genus was at first referred by its founder to the Creodonta—Carnivora 

 Primigenia {supra, Part I.). 



