30 GEOLOGICAL SURVEY OP TEXAS. 



rior border of the posterior lake of the last superior molar. The facial 

 plate of the maxillary is not preserved to the orbital border, but ex- 

 tends sufficiently near to show that there was no preorbital fossa. 



Measurements . 



Hm. 



Total length of six molars 89 



Length of true molars 44 



Diameters of ]\[. i J anteroposterior 14 



( transverse ? 18 



Length of grinding face of P. m. iii 19 



The measurements of the other molar teeth are a little less than the 

 above. In one of these two superior molars are in place in the jaw. 



I can not help suspecting that this species will turn out to have been 

 established on teeth of the P. placidus in an advanced stage of wear. I 

 discuss this question more fully under the head of that species. 



PROTOHIPPUS FOSSULATUS, CopC. 



Sp. nov. Plates V, VI, VII. 



Represented by a cranium, which has lost all posterior to the posterior 

 frontal region and anterior to the premaxillary border, found by Mr. W. 

 F. Cummins in the Loup Fork formation of Donley county, Texas. 



The dimensions of this species are superior to those of any other mem- 

 bers of the genus excepting the P. pachyops and P. mirabilis. It equals 

 the former and is a little exceeded by the latter. The characters of the 

 lateral facial fossae are peculiar, and as they are exactly alike on both 

 sides of the skull, I believe them to be normal. There is no fossa imme- 

 diately in front of the orbit, but there is a narrow and deep maxillonasal 

 fossa, whose posterior extremity approaches nearer to the superior part 

 of the orbit than any other. Beneath it, and immediately above the 

 penultimate molar tooth, is a small but well pronounced fossa, which is 

 about as large as would be produced by an oblique impression of the end 

 of the thumb in putty. Immediately anterior to the infraorbital foramen 

 is a wider and shallower fossa. Anterior to this is a fossa directed ob- 

 liquely downward and forward, as a continuation of the nasomaxillary; 

 and below and in front of this one is a deep concavity of the alveolar 

 border. 



The posterior wall of the orbit is transverse, thi'Owing the border 

 outwards. The malomaxillar}'^ ridge is prominent, but is obtuse below 

 the anteorbital region, and the small preorbital fossa, below whose an- 

 terior border it terminates; that is above the first true molar. The posi- 

 tion of the infraorbital foramen is elevated, and is above the anterior 

 border of the first true molar. The anterior border of the orbit is ^bove 

 the posterior border of the last superior molar. 



