VERTEBRATE FAUNA OF THE LOUP FORK BEDS. 23 



The Wyoming molars resemble closely the fragmentary specimen fig- 

 ured and described by Leidy as AncMtJierium australe,* which was found 

 in Washington county, Texas, in the southern central part of the State* 

 It was found in association with an superior molar of the Protohippus per- 

 ditua, according to Leidy, and very probably is a deciduous tooth of that 

 species. The Anchippus brevidens, Marsh, is also apparently founded on 

 the deciduous molars of some species.! 



The Geological Survey collection contains the dlmost perfect crarliunl 

 of a colt which was found at the same limited locality as that which pro= 

 duced the Protohippus pachyops and P. fossuldtus; and from its characters 

 I suspect that it belongs to the former species. The molar teethj which 

 ai'e all present (four in number), resemble closely those described by Leidy 

 as Parahippus cognatus, differing only in their considerably larger sizci 

 This is true of the last tooth of the series, while the others resemble more 

 nearly the Hypohippus affinis. There can be no doubt then that these 

 supposed genera were founded on milk teeth of Protohippus. The speci- 

 men of P. cognatus described by Leidy belongs to one of the medium 

 sized Protohippi, as P. labrosus, etc., while H. affinis belongs to one of 

 the larger forms. 



The material at my disposal which represents this genus consists of 

 numerous specimens from Nebraska, Kansas, Oregon, Montana, and Texas. 

 Of the ten species here adopted, seven are represented by private collec- 

 tion, and six were obtained by the party of the Geological Survey of 

 Texas, under the direction of Mr. W. F. Cummins, in the northwestern 

 part of the State. 



The species may be distinguished by the following characteristics, 



I. No preorbital fossa. 



Lake borders at first plicate; true molars 85 mm.; facial 



ridge very obtuse P. pachyops 



Lake borders at first plicate; true molars 61 mm.; principal 



premolars 67 mm. ; fourth premolar one-rooted P. perditus 



True molars 43 mm P. medius 



True molars 44 mm.; principal premolars 45 mm.; enamel 



simple in adults P. parvulus 



II. A small preorbital fossa well anterior to the orbit. 



True molars 69 mm.; enamel simple, facial ridge obtuse. . .P. fossulatus 



III. A large preorbital fossa closely approximated to the orbit. 

 True molars 55 mm. ; principal premolars 62 mm. ; slightly 



plicate in the young; premolar one-rooted; facial ridge 



acute p. sejunctus 



♦Report U. S. Geol. Survey Terrs., 1, 1873, p. 250. Plate XX, figure 19. 

 fAmer. Journal Science and Arts, VII, 1875, p. 254. 



