400 THE PUERCO EPOCH. 



degree. There is a short lateral focet on the inner side for the navicular. 

 The extemal tendinous tuberosity is prominent, and extends across the infe- 

 rior face of the bone. The front of the ectocuneiform is slightly oblique ; 

 it is half as high again as wide, and has a low tuberosity near the internal 

 proximal corner. Posterior tuberosity large. The metatarsals are short. 

 The third aiul fourth are of equal lengths; the second is a little and the 

 first much shorter. The proximal extremity of the fourth is externally con- 

 cave for the head of the fifth. There are no deep transverse grooves above 

 the distal condyles These are rather narrow, and have a short posterioi" 

 heel. The distal faces of the phalanges are infero-posterior, but on the 

 plialangines they are somewhat recurved. The lateral ligamentous fossae 

 are moderate. The phalanges are slenderer than is usual in ungulate mam- 

 malia, and resemble those of some carnivora. They are move depressed 

 than in these animals, and resemble most those of Mesonyx. The distal 

 extremities of the metapodials, though narrow, display no tendency to the 

 convex form seen in carnivora. 



It is evident from the propox'tions of the posterior feet in the two speci- 

 mens preserved, that these members are relatively small in the Periptijclms 

 rhabdodon. It is also evident that they were wide and flat and plantigrade; 

 more so than in the species of Phenacodus. 



Measurements of posterior foot. 



No. 1. 



M. 

 Width of calcanenni at snstentacnlum 026 



Diameters 8n8tentacular facet ^""♦«^''P''«*«"°'" 0^3 



( transverse 013 



DiHtal width of calcanenni (134 



Diameters cnboid facet ^ ''^'^'"'''^ 01^' 



< transverse 017 



Astragalns; greatest l'''"St'> O^^* 



*■ ' *• \ width (»-ja 



( length 010 



Trochlea of astragalus; KreatCHt < width 023 



' height, externally 014 



Head of astragulns, greatest J '^"*"' ^-"^ 



( litight 012 



Length of third metatarNal 050 



1 ]>ruxiuiully auteroposteriorly 015 



Diameter of third raetatarsau medially transversely 009 



( at distal fossa; transversely 0135 



Length of fourth metatarsal 046 



