122 



UNGULATA 



ORDER VII 



Frotogonodon Scott {Miodaenus pentacus Cope). 



This very large form, with 

 quinquetubercularm olars, 

 is perhaps ancestral to cer- 

 tain artiodactyls, such as 

 Achaenodon and Entelodon. 

 Lower Eocene ; Puerco 

 beds, New Mexico. 



Fig. 152. 



Tetradaenodon piiercensis Cope sp. 

 Lower Eocene of Torrejon beds, New 

 Mexico. A, Upper molars. B, Lower 

 molars (1)4, il/i.o,P4). Vi- (After Osborn.) 

 C, Hind foot. Va- (After Matthew.) 



Fig. 153. 



Meniscotherium terrae-rvbrae Cope. 

 Wasatch Strata of Lower Eocene, 

 New Mexico. The three upper 

 molars and last two premolars, i/i. 

 (After Cope.) 



Family 4. Meniscotheriidae Cope. 



Tooth series nearly continuous. Superior molars quadritubercular, with V^-shaped 

 edoloph, two crest-like curved intermediate tubercles, and two unequal conical internal 

 cusps. Posterior premolars trituiercular. Inferior molars and last premolar com- 

 posed of two V-shaped crescents, the three anterior premolars simple. Astragalus 

 strongly elongate, the distal articular surface rounded. 



Meniscotherium Cope {Hyracops Marsh) 

 (Figs. 148, 153). Lower Eocene (Wasatch 

 beds) ; New Mexico. 



Family 5. Pleuraspidotheriidae Lemoine. 



Dentition complete. Incisors, canines and 

 first premolars conical. A small diastema be- 

 tween the first and second or third premolars. 

 Superior molars, with four y -shaped cones and a 

 weakly developed protocomde. Fourth premolar 

 like the first molar ; third premolar with simple 

 internal conical tubercle. Inferior molars, as well 

 as third and fourth premolars, with four conical 

 -B, Lower molars. '/,. (After tubevcles in pair s and one odd anterior cusp. Feet 

 pentadactyl ; terminal phalanges slender with slight 

 lateral wing-like expansions distally. Astragalus with broad trochlea and short neck. 



Pleuraspidotherium Lemoiue (Fig. 154). This form, from the Lowermost 

 Eocene of Cernays, near Eheims, may possibly have phylogenetic relations 

 with European perissodactyls. 



Suborder B. LITOPTERNA Ameghino.^ 



Extinct, digitigrade ungulates with serially arranged carpcds and tarsals, manus 

 and pes with five (?), three or one digits. Astragalus with deep trochlea and convex 



^ Ameghino, Flor., Coutribucion al conocimiento de los mamiferos fosiles de la Republica 

 Argentiua. Actas Acad. Nac. Cordoba, 1889, vol. vi. — Sur les ougules fossiles de I'Argeutine. 



Fig. 154. 



Pleuraspidotherium aumoiiieri Lemoine, 

 Lower Eocene, Cernays, near Rheims. A, 

 Upper molar " ' " " 



Lemoine.) 



