36 



THE MERYCOIDODONT1D/E 



The skull has suffered crushing from above, and this may have somewhat increased the bizygomatic 

 diameter, thus making the skull more mesocephalic than dolichocephalic. The malar and squamous 

 portions of the zygomatic arch are of nearly equal depth, and the posterior portion rises very gently 

 and very slightly. In consequence the arch is nearly parallel with the dentition. The unreduced 

 nasals extend forward to a point above the incisor border. The premaxillaries are reduced and appar- 

 ently do not meet in the sagittal plane. The lacrimal fossa is absent. The frontals were presumably 

 moderately flat, with the decurvature above the orbits. The downcrushing, already referred to, 

 makes the superior skull surface abnormal. The orbits have small postorbital processes, as in 

 P. minor j from the frontal and malar. The temporal ridges unite just back of the postorbital con- 

 striction to form a long, thin, but not especially high sagittal crest about a third of the skull length. 

 The brain case is unusually long and narrow. The basicranial axis is moderately steep. The glenoid 

 articular surface is gently convex, and the postglenoid process is stout and anteroposteriorly com- 

 pressed and has a moderately oblique external border. Index: 0.54a. 



Mandible: The symphysis is rather peculiarly shaped. In profile it is strongly convex above 

 and below, with a concavity which lies beneath the mental foramen. The symphysiodental angle is 



Fig. 11. — Protoreodon faradoxicus (Scott). 

 Crown view of left superior dentition. HT. Cat. 

 No. 11234 P.U.M. Nat. size. (Redrawn from 

 Scott, 1899.) 



oo 



Fig. 12. — Protoreodon farvus Scott and Osborn. 

 Crown view of left superior dentition. PT. Cat. 

 No. 11535 P.U.M. Nat. size. (Redrawn from 

 Scott, 1899.) 



approximately 48°. The inferior border of the horizontal ramus is nearly straight and the angle 

 not prominent. The posterior border of the ascending ramus is rugose, the condyle is moderately 

 high and is above the anterior part of the angle, the sigmoid notch is small, and the coronoid process 

 is not much elevated above the condyle. The masseteric fossa is deep but not very extensive. 



Foramina: The large infraorbital foramina are above the middle of P 3 . 



Dentition: Superior: The incisors are small, with only one on a side, according to Scott, while 

 the canine is large, recurved, and trihedral. The premolars are simple. The internal cingulum is 

 large on P 4 and M 2 and less well developed on M 1 and M 3 . The parastyles and mesostyles are about 

 equally well developed in this species, as they are in P. fumilus and P. farvus. P 2 is similar to that 

 of P. minor, with a poorly developed posterior crescent. P 3 is anteroposteriorly shorter and wider 

 than that of the latter species, while P 4 has practically the same structure as that of P. fumilus. 



Discussion: This species appears to have but one superior incisor, and certainly the premaxil- 

 laries are reduced so that they do not meet in the mid-line. My thought is that perhaps the median 

 pairs of incisors have been lost because of their tiny size, but of this I cannot be sure until more 

 complete material is recovered. Should there finally prove to be but one incisor on each side, my 

 feeling would be that a new name should be proposed for the reception of this species with the rank 

 of a subgenus under Protoreodon. Agriotherium is preoccupied. 



It is possible that P. faradoxicus is approaching Hyomeryx, in which genus the premaxillaries 

 are very much reduced and seemingly no superior incisors are to be found. In all other characters 

 P. faradoxicus is typical of Protoreodon. I believe that in all of the species of Protoreodon the 

 contiguous premaxillary surfaces were very small and were easily broken away before fossilization, 

 which may account for the apparent lack of contact in the sagittal plane, at least in some instances. 



