Diameters of second true molar . 



. transverse 015 



i a, 

 Diameters of third true molar . 



transverse 019 



174 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol. YI. 



Measurements of sJcull. 



Total length from left side of inion to front of canine 147 



From same to end of maxillary bone 075 



From same to palatal notch 087 



Length of diastema Oil 



Length of molar series 059 



Length of true molars , 035 



c antero-posterior 013 



( antero-posterior - 015 



The linear measurements of this skull are three-fourths that of G.ferox, 

 and three-fifths that of G. macrocephalus. 



Found by J. L. Wortman, on the John Day Eiver, Oregon. 

 Dedicated to my friend John A. Ryder, of PhiladeliDhia. 



Pal^ochcerus platyops sp. nov. 



Established on a nearly complete skull, which lacks the muzzle ante- 

 rior to the third premolar teeth, the lower jaw, and parts of the zygomata. 

 The last superior molar is not protruded, and it is probable that the 

 fourth deciduous i^remolar still remains in the jaw. 



The size of this species exceeds that of any other member of the genus- 

 The postorbital process is also more elongate, so as to inclose the orbit 

 to a greater extent than is usual in Palceochcerus, The temporal ridges 

 are strong, and rise into a convexity above the anterior part of the tem- 

 poral fossa. From this point they converge gradually to form the sagit- 

 tal crest, which has a truncate edge. Between the ridges the surface is 

 concave, the basin widening forwards as far as a line passing through 

 the posterior third of the orbits. The frontal bone rises steeply from the 

 orbit to the edge of this basin, and is regularly convex in front of it. 

 The profile descends forwards, so that the section at the infraorbital, 

 foramen is broadly convex, and not compressed, as in the species of 

 Fcdceochoerus from the Truckee beds of Oregon. The emargination of the 

 palate extends as far forwards as the line of the anterior border of the 

 second true molar. The posterior border of the infraorbital foramen is 

 above the middle of the anterior root of the fourth premolar. The post- 

 glenoid, mastoid, and postparietal foramina are present ; the last named 

 rather small and in the inferior part of the parietal bone. 



The base of the fourth premolar is remarkably extended antero-pos- 

 teriorly. Its crown has a posterior basal cingulum, and is in contact 

 with those of the molars anterior and posterior to it* The crown of the 

 first true molar is narrowed inwards, the anterior border being more 

 oblique than the posterior. Both of these borders have a wide cingu- 

 lum. There are two large external cusps, with antero-posterior continu- 

 ous edges, two smaU median cusps, and a larger internal cusp. No 

 internal or external cingula. The second true molar is also narrowed 

 inwards, but less so than the first, and the posterior border is the only 



