504 GEOLOGICAL SUEVEY OF THE TERRITOKIES. 



third is four-lobed. Third premolar with large anterior lobe and pos- 

 te4or heel. Median lobes obtuse ; three last lobes connected by a low 

 edge. Enamel slightly rugose. 



Measurements. 



M. 



Length of bases of tliree premolars 0.076 



Length of basis of third premolar '. 008 



Elevation of crown of third premolar - 004 



Dex^th of ramus at third premolar ■. 007 



PELONAX, Cope. 



This genus embraces species which are nearly allied to Elotlierium. 

 It is more hippopotamoid than that genus, in the i)ossession of four 

 digits on all the feet and a rudimentary fifth on the pes. According to 

 Kowalevsky, Motheriuvi possesses but two digits of the fore-foot. The 

 U. mortonii and U. ingens of Leidy represented the genus during the 

 Miocene period in IsTorth America, species which Kowalevsky is disposed 

 to unite with the E. magnum^ Aym., of Europe. 



PelonAX crassus, Marsh. {%) Elotlierium crassum, Marsh, Amer. 

 Journ. Sci. and Arts, 1873, p. 487. 



According to Marsh, the digits in this species are 4-5. Three crania, 

 one nearly complete, represent this species in our collections, so far as I 

 can determine from Marsli's very brief description. The form of the 

 skull is very different from that of the Elotlierium mortonii. The poste- 

 rior portion from the orbits is abbreviated and the sagittal crest de- 

 scends from the protuberant frontal region. The orbits present upward 

 and forward, and the temporal fossa is higher than long ;. the face and 

 muzzle are long and narrow. The malar portion of the zygoma is con- 

 siderably deeper than the squamosal portion. The descending i^rocess 

 of the zygoma is directed downward and forward, as described by 

 Marsh. There is a small, supernumerary, single-rooted premolar close 

 behind the second in all three crania. The length of one of the skulls 

 is eighteen inches. The measurements of the teeth agree with those 

 given by Marsh. 



Pelonax ramosus, Cope ; Elotlierium ramosum, Cope, Bull. U. S. 

 Geol. Surv. Terrs., 1874, No. 1, p. 27. 



Established on the greater part of a mandible with teeth, from a cra- 

 nium, which, when complete, must have measured nearly two feet and a 

 half in length, indicating an animal no smaller than the largest living 

 rhinoceroses. The species is remarkable for the great size of the tuber- 

 osities on the under side of the mandibular rami, especially of the ante- 

 rior pair. The symphysis is narrow and deep in front, and the tuber- 

 osities form two branches, whose bases occupy the entire lower part 

 of its infero-anterior face. They are some inches long, and are directed 

 outward and downward. The posterior edge is acute, and the extremity 

 very rugose, as though for the attachment of a horny or cartilaginous 

 cap or apex. The outer face is flat; the inner, convex. The second tu- 

 berosity is below the first true molar, and is flat and with apex obtuse 

 in profile, and turned outward. The molar teeth number seven ; the 

 first and second of the four premolars have but a single root, and are 

 separated by a short diastema. The tubercles of the molars are low ; 

 the crowns of some of the x)remolars have a cingulum in front and be- 



