CONDYLAETHRA. 391 



as regax'ds the family of Arctocyonidce. The only suggestion of such affinity 

 is found in the form of the astragalus, and in the narrow external phalanges. 

 The astragalus of all the Condylarthra is undistinguishable from that of the 

 Creodonta. It is almost certain that the middle ungual phalanges in Perip- 

 tychus are much wider than the lateral ones, so that they are probably truly 

 ungulate. The reference to the Condylarthra is indicated by the large infe- 

 rior third trochanter of the femur ; also by the vertical aspect of the man- 

 dibular condyle, with the identity of plane of the angular and coronoid plates. 

 In the Creodonta, where this part is known, the coronoid pi'ocess and the angu- 

 lar plate are, as in Carnivora, different. I except from this Ilesonyx, where 

 they are in the same plane. 



There are three species of Periptychus, two of which differ principally 

 in dimensions. 



Periptychus rhabdodon Cope. 



American Naturalist, Sept. (Oct. ), 1882. Catatklcerhua rhabdodon Cope. American Naturalist, 1881, 

 October, p. 830 (Sept. 22). Paleontological Bulletin, No. 33, p. 487, 1881. Proceed. Amer. Philo. Soc, 

 1881, p. 487. 



Plates XXIII f, XXIII g, figs. 1-11 ; LVII f, figs. 1-2. 



This species was evidently very abundant during the Puerco epoch, 

 portions of fifty individuals having come into my possession. These consist 

 mostly of fragments of the jaws, superior and inferior. The most important 

 of these specimens includes most of the dentition of the mandible and the 

 posterior part of that of the maxillary bone ; fragments of the skull ; a 

 number of vertebrae ; considerable parts of both limbs ; part of the posterior 

 foot. A second specimen includes both jaws, parts of scapula and ulna, 

 cervical vertebrae, femur and part of posterior foot. A third specimen in- 

 cludes part of the lower jaw with condyle and teeth ; some vertebrae, and 

 the astragalus. Another includes one mandibular ramus with symphysis. 

 There are many maxillary bones with teeth, but no premaxillaries. 



All the teeth of this species (incisors unknown) are characterized by 

 a remarkable sculpture of sharply-defined grooves and ridges. The ridges 

 extend from the bases of the crowns to the apices of the cusps of the pre- 

 molars and molars, and on the external sides of the teeth are straisrht. 

 As they converge some of the ridges cease. On the interior faces of the 

 crowns the grooves are less profound, and the ridges are more irregular in 



