VEJElTiEteRAtK FAUNA OF THE LOUP FORK BEDH. 29 



wanting from the two other molars. Ill this poiilt this tooth res6mbl^s 

 the tooth described by Leidy as AnchippuSj while the two others al-e 

 identical in all respects with his itypohippus. The first molar is rela- 

 tively small, as in the permanent dentition^ but it differs from the latter 

 in having a strong internal crest, which is nearly as elevated as the ex- 

 ternal, and is separated from it by a deep fossa. 



Measwements. 



* Mm. 



Total length of skull preserved from inion 290 



From inion to posterior bonier of orbit (axial) 115 



From inion to infraorbital foramen 242 



Horizontal diameter of orbit 48 



Width of skull at zygomatic arches 124 



Width of skull between middle of orbits 81 



Length from inion to palatal notch 210 



Width below at D. m. i 44 



Width below at front of D. m. iv 56 



Width of palate at D. m. ii 14 



Width of palate at D. m. iv posteriorly 32 



( anteroposterior 16 



Diameters of D. m. i. ... -j ^,.^,^^^g^g^ 14 



anteroposterior 33 



( an 

 "•••■jtr, 



Diameters of D.m. ax..., .j.^nsverse 27 



teroposterior 30 



( an 

 I trii 



Diametersof D.m.iv..., .......g^erse 28 



Excepting in the case of the first molar, the dentition is much simpler 

 than that of the adult, and is identical, each tooth taken by itself, with 

 that of the genus Anchitherium. Their almost unworn condition is espe- 

 cially favorable for the exhibition of this resemblance. 



PROTOuippus PERDiTDS, Leidy. 



Plate X, Figure 2. For synonymy see above. 



A single fragmentary superior molar is the only indication of this spe- 

 cies which was obtained by the Survey from the locality of Donley county. 

 It is evidently not common at this place during the Loup Fork epoch, 

 contrary to what obtains in more northern regions, where it is the most 

 abundant species. 



PROTOHipptis PARVULUS, Marsh. 



Plate XI, Figures 1, 2. For synonymy see above. 



I found superior molar teeth of this species at three localities; one of 

 the specimens consists of the maxillary bone of the right side, with all the 

 molars except the fourth premolar in place. The animal is adult, as the 

 anterior lake of the first true molar is obliterated by wear. The enamel 

 border of all the lakes is simple, except that there is a loop on the postO' 



