#60 APPENDIX. 



plays no diastemata (spaces) behind the superior canines, while 

 in the latter there are two. This fossil (from New Mexico) was 

 first described by him under the name Hyracotherium tapiri- 

 num, but the discovery of better specimens demonstrates its 

 claim to the rank of a new genus. 



PHENACODUS. 



Phenacodus, one of the most important of recent paleon- 

 tological discoveries, was first made known by Prof. Cope in 

 1873,* from several molar teeth which he obtained from the 

 New Mexican Wasatch. Its systematic position in the mam- 

 malian class was, however, involved in considerable uncertainty 

 till the discovery of the greater part of the skeletons of two 

 distinct species of this genus by the writer in the Wyoming 

 Wasatch during the summer of 1881, which afforded Prof. 

 Cope the means of determining its true position and elucidat- 

 ing the many important and interesting points its osteology 

 teaches.f It possesses five well developed toes in functional 



* Paleontological Bulletin, No. 17, Oct. 1873, p. 3. 



t Prior to the discovery of these skeletons no characters had been found 

 among the Ungulata which indicate a group connecting the Perissodactyla 

 with the elephants and hyrax.* But it is now necessary to create a new 

 order, which Prof. Cope designates the Condylarthra. (Paleontological 

 Bulletin, No. 34. Dec. 1881, p. 177). The characters on which this division 

 reposes are found in the carpus and the astragalus (hock or ankle hone) 

 and their manner of articulation. The Perissodactyla are distinguished by 

 the fact that the scaphoid articulates with two bones below, and the astra- 

 galus articulates inferiorly by two nearly flat facets with the cuboid and 

 navicular bones. They are divisible into ten families, including forty -eight 

 genera, variously distributed throughout geologic time ; but as only four 

 of these families concern us for the present, I will spare the memory of the 

 reader by not discussing the classification of the others. The first to which 

 attention may be directed is the Lophiodonticlce, embracing eight well de- 



* A gray-haired, rabbit-sized pachyderm, with 4 toes on the forefeet, 3 

 on the hind, a mere tubercle for a tail, molars resembling (in miniature) 

 those of the rhinoceros, 2 large, triangular, curved, tusk-like incisors in the 

 upper jaw, and 4 straight ones in the lower. Ctivier says the upper jaw, in 

 youth, has 2 small canines, but Marsh's dental formula is: Incisors, 12, 

 12 ; canines, 00, 00 ; premolars, 4 4, 44 ; molars, 33, 33=34. 

 There are sevei-al species, the African being able to climb a tree. The 

 Cape hyrax is called the rock-badger or rock-rabbit. The hyrax was long 

 classed among the rodents, and was also called a miniature rhinoceros. 

 There are various affinities between the elephant and some rodents (1) in 

 the size of the tusks ; (2) in the molars being often formed of parallel lam- 

 inae ; (3) in the form of several of their bones. 



