Peterson: Material Discovered in Uinta Basin. 105 



Principal Generic Characters: J^f , C\, P?|-", Mf . Premaxillaries 

 extended well foncard and anterior nares oblique, quite large, and con- 

 tinued backii'ard into a distinct air-sinus analogous to that in the recent 

 tapir. Nasals somewhat reduced in length. Skull and lower jaws 

 gently constricted back of the incisors and canines. Superior canine 

 isolated by diastemata. Infra-orbital foramen large and located well 

 back. Sagittal crest prominent. P~ much reduced. P- with slight 

 indication of two internal tubercles. P- with large single deuterocone. 

 Upper molars ivith sharp cross-crests and deep valleys. Parastyle 

 small and sessile, m^tacone trenchant and the external face not convex. 



Symphysis of mandibular rami solidly codssified. Hypoconulid of 

 Mj small. Absence of connecting crest between proto- and hypoconids 

 Limbs slender. Astragalus high, narroiv, trochlea oblique, equine-like.''^ 



Specific Characters: P- with little or no indication of a tctracone; 

 styles at the exit of the median valley of the superior molars relatively 

 large; cingula on anterior and posterior faces of upper molars prominent; 

 animals about half the size of a sh'eep. 



General Description of the Type. Skull and Lower Jaivs: 

 Since Professor Marsh's preliminary description of Helaletes boops 

 {I.e., p. 218) was published, the entire specimen has been skilfully 

 prepared and it is now possible to furnish a more complete description. 



From the generic characters it is at once evident that these remains, 

 and especially the skull, possess remarkable similarities to the tapir. 

 We have for instance the prominent sagittal crest, the broadness of the 

 anterior portion of the frontals, and posterior portion of the nasals, 

 the reduced antero-posterior diameter of the latter bones, the large 

 premaxillaries, the oblique borders of the anterior nares, the large 

 infra-orbital foramen and, above all else, the characteristic large 

 excavation on the side of the face formed at the expense of the maxil- 

 lary and the nasals (See PI. XLIII, Fig. i). This air-sinus, so far as 

 can be determined from the crushed specimen, appears to directly 

 communicate with the anterior nares, as in Palccotherium medium, 

 and the tapir. As already stated the base of the nasal has a consider- 

 able lateral contact along the anterior termination of the frontal and 



"2 See Leidy's description and illustration of " Hyrachyus" nanus in the "Extinct 

 Vertebrate Fauna," pp. 68-69, PI- XXVI, Fig. 11. Also Scott; Contrib. E. M 

 Museum, Bull. No. 3, 1883, p. 51. PI. VIII, Fig. 4. 



"^ The character of the astragalus was already pointed out by Prof. Marsh in his 

 original description (p. 218). 



