I 28 Bulletin American Museum of Natural History. [Vol. XIV, 



forms an acute ridge bounding the internal face of the crown posteriorly. This 

 encloses with the metastylid a flat open gutter as wide as the metastylid. A 

 sharp ridge marks the internal face of the anterior border, but it is closely ap- 

 pressed to the metaconid, which it does not equal in elevation." 

 Measurements given. 



Length of crown preserved 37 '"ni- 



Antero-posterior diameter at middle 16.5 



Transverse diameter at metastylid 8 



Transverse diameter in front of metastylid 6 



This tooth shows the same characters pointed out in Cope's E. 

 eurystylus to distinguish it from the genus Equus except that the 

 little fold of enamel at the anterior border of the protoconid is 



wanting. A comparison of 

 Cope's figure (reproduced in 

 7/H'^=''~~'l Figure 18, and Figure 19 

 which represents a corres- 

 ponding lower molar of jPr<7- 



Fig. 18. Type of Pig. ig. Lower ^ " 



Protohi/>pus phlegon molar oi Protoki/>ptis toklppUS, ^O. lO^"] QyQoW. Km. 



(Egutis mitiutzisCo-pe). j/. (Loup Fork). 



Lower molar. (After MuS.,) shoWS the Very cloSC 



relationship of the species to 

 which the teeth represented by these figures belong, and were it not 

 for the little enamel fold mentioned above, in the one, they would 

 undoubtedly be referred to the same species if their different lo- 

 calities were not known. In a series of five lower teeth (No. 10626, 

 Coll. Am. Mus.) of this species, found in the exact locality 

 in the Blanco beds from which Cope's type specimen was taken, 

 the same general Protohippus-like characters are shown as in 

 the type tooth, and a rudiment ofjthe enamel fold of the protoconid 

 is shown in all of them. 



Very unfortunately, an upper molar, found by the writer in 

 the same locality a few days before the finding of the lower teeth, 

 was lost. This tooth agreed in size with the lower teeth and 

 could not have been distinguished from Protohippus. The 

 crown was not much worn and the little oval protocone was still 

 quite separated from the protoconule. 



The species distinctions of this little horse of the Blanco beds 

 apparently cannot be defined, unless the rudimentary condition 

 of the anterior outward fold of enamel of the protoconid should 

 prove to be constant and thus separate it from the species of 

 Protohippus from the true Loup Fork beds. 



