Cope.] 



382 



[April 15, 



North America and Europe 

 rium, Pliolophus. 



Fig. 1. Pait of iiiiht maxiilaij bone of 

 Pachynolovhiis smgulai it Cope; fiom the 

 Wasatch beJs of New Mexico, from Capt. 

 Wheeler's report iv ii pi. Ixvi. 



Pachynolophus, Uyrachyus, Hyraeothe- 



Europe only ; LopModon, Lo- 

 phioiherium. 



Four of the genera ascribed 

 to North America have come un- 

 der my observation. 



TRIPLOPID^. 



Cope, American Naturalist, 

 1881, April (March 25th), p. 340. 



But one genus of this family 

 is known at present, but the 

 number will probably be in- 

 (jreased when the structure of 

 the feet of various imperfectly 

 known species is ascertained. 



TRIPLOPUS Cope. 



American Naturalist, 1880, p. 383 (April 27th). 



Dental formula, I. ? ; C. | ; P-m. ; | ; M. f ; a considerable diastema 

 anterior to the first premolar. Molars with only two vertical external 

 ridges, the anterior eingular and the approximated median of the anterior 

 crescent. Transverse crests two, uninterrupted and rather oblique ; a 

 ? third and short crest, on the posterior base of the first true molar. Pre- 

 molars different from molars, the third and fourth with two transverse 

 crests. Inferior molars with two transverse crests, as in LopModon, the 

 last without heel. 



An ossified inferior wall of the meatus auditorius externus. Posttym- 

 panic and paroccipital processes distinct form each other. No postorbital 

 arch. Postparietal and mastoid foramina preserved ; the latter large. 

 Cervical vertebrae rather long; axis with subcylindric odontoid process. 

 Scapula with small coronoid process. Great tuberosity of humerus long, 

 curved. No trochlear crest on condyles of humerus ; epicondyles rudi- 

 mental. Ulna and radius distinct throughout their length ; ulnar articula- 

 tion with carpus, small. Trapezoid bone of carpus with a facet for the 

 trapezium. Unciform with two inferior facets. Metacarpals three principal 

 ones, and one, the fifth, rudimental ; the distal extremities of the second 

 and fifth opposite ; the third a little longer. 



The dentition of this genus is nearly that of Hyrachyus. The only ex- 

 ception is the possible third transverse crest of the first true molars*. The 

 other portions of the skeleton known, are also much like those of 

 Hyrachyus, with the exception of the number of digits of the anterior foot. 

 The entirely rudimental character of the fifth metacarpal, which with its 



*Thls point is further considered in the description of the species. 



