PROMERYCOCHCERUS 127 



Mandible: The chin profile shows a very slight concavity and no mental eminence. The 

 symphysiodental angle is 47°. The inferior border of the horizontal ramus has a slight convexity 

 below the anterior molars. The angle is moderately large. The posterior border of the ascending 

 ramus is thick and is straighter than in some of the other species of this genus. The condyle is gently 

 convex anteroposteriorly, the sigmoid notch shallow, and the coronoid process thin and low. 



Foramina: The infraorbital foramina lie above the interval between P 3 and P\ The supra- 

 orbitals are about 1 5 mm. apart. The foramen ovale is large and appears to be double on the left 

 side. If the foramen rotundum is present, it is very small. As in other species, the posterior 

 palatines are not visible. 



Dentition: Superior: The metastyle of M 3 is small but very distinct and demarcated from the 

 metacone. All of the molars, as well as P 4 , bear prominent internal cingula. P 4 has an antero- 

 external pit. The posterior crescent of P 3 is large, and the posterior, anterior, and anterointermediate 

 crests are well developed, but the median crest is weak. The posterior crescents on P 1 and P 2 are 

 large, but the anterointermediate crests are thin and small. P 1 is isolated. The incisors are not 

 spaced. The canines are large and strong. Inferior: The metastylid of M 3 is very large. The 

 premolars are somewhat crowded but typical in construction. Pi is lenticular and somewhat pre- 

 molariform, suggestive of the condition found in Aletoreodon, though in the latter this is carried to 

 a much greater degree. The lower incisors are not spaced. The superior molar-premolar index 

 is 0.907 and that of the inferior series 0.83. 



Discussion: I tentatively consider that this species may represent the female of P. hollandi. 

 In any event, I should reduce it to a subspecies of that form at present. 



Promerycochoerus hollandi minor Douglass 1903 

 Fig. 83 j PI. XVI 



Original Reference: New vertebrates from the Montana Tertiary. Ann. Carnegie Mus., II, pp. 

 168-170,%. 12. 



Type Locality: Near Drummond, on the Hellgate River, Montana. 



Geologic Horizon: Lower Miocene (lower Harrison). 



Type: Holotype, Cat. No. 769 CM., large part of a skull and mandible, with upper and posterior parts, 

 together with posterior part of ascending ramus, missing. All teeth represented but I 1 . 



Specific Characters: I judge the skull to be slightly smaller than that of P. vantasselensis 

 ■pygma?us, with about the same general proportions. The maximum zygomatic expansion is at the 

 posterior of the zygomatic foramina. The malar portion is of medium size, and the convexity from 

 the anterior zygomatic pedicle turns sharply upward in front of the orbit. The malar has less depth 

 than that in P. montanus, P. macrostegus, or P. leidyi, and the inferior border is grooved. The 

 anterior part of the squamous portion is pointed and lies below the postorbital bar. From here it 

 descends somewhat and then rises abruptly, but less steeply than in P. macrostegus or P. superbus. 

 It is moderately slender, and the outer border is somewhat thickened and rounded. The nasals are 

 long and appear to be posteriorly truncated. The lacrimal fossas are small and shallow. The 

 frontals are wide and appear to be unreduced, with the usual decurved portion above the orbits. 

 These orbits are subcircular, with the greater diameter vertical. The palate is wide. The glenoid 

 articular surface is moderately small. The bulls were large, according to Douglass, and the paroc- 

 cipital processes small, with only a slight expansion at their bases. Index: 0.70a. 



Mandible: The symphysis is short and had no mental tubercle. The symphysiodental angle 

 is 45°. The horizontal ramus slopes downward and backward more markedly than usual in this 

 genus. 



