MERYCOIDES 173 



descends gradually to the angle. The condyle is distinctly convex anteroposteriorly and is not offset 

 from the ascending ramus. The coronoid process is slender and rises but slightly above the condyle, 

 while the sigmoid notch is very shallow and wide open. The masseteric fossa is moderately large — 

 much larger than in Pronomotherium. 



Foramina: The infraorbitals are above the interval between P 3 and P 4 . The supraorbitals lie 

 about in a plane through the center of the orbits, fairly close to the median suture. Douglass 

 stated (1907C) that there is a foramen rotundum just anterior to the foramen lacerum medium. I 

 believe that this is an error, due to the insufficient cleaning of the skull at the time of description. 

 As I interpret the foramina in this area, there is a small foramen lacerum medium anterointernal 

 to the bulla, a large foramen ovale in front of the bulla, and, in advance of that, the foramen lacerum 

 anterius. 



Dentition: The teeth are brachyodont and, although moderately worn, do not seem to have 

 any tendency to hypsodonty. The superior molar series is slightly longer than the premolar (index 

 0.87). The superior and inferior canines and the incisors are small. The dental series tend to 

 converge slightly forward. M 3 has a small posteromedial lobe. 



Skeleton: The limbs and feet are rather slender, with proportions similar to those of Lim- 

 nenetes and less slender than in Merychyus. 



Merycoides latidens (Douglass) 1907 

 Fig. 125; PI. XXVI 



Original Reference: Some new merycoidodonts. Ann. Carnegie Mus., IV, pp. 102-103, pi. 25 

 (Mesoreodon(?) latidens'). 



Synonym: Mesoreodon laticefs Loomis 1924 — undoubtedly a misprint for latidens. 



Type Locality: Missouri River, about 20 miles east of Helena, Montana. 



Geologic Horizon: Lower Miocene (lower Harrison). 



Types: Holotype, Cat. No. 908 CM., skull and jaws, the former practically complete and the latter lack- 

 ing the angles. Collected by E. Douglass in 1902. Paratype, Cat. No. 1234 CM., skull which may have 

 belonged to a female, as it is slenderer than the holotype. Both skulls somewhat crushed vertically. 



Specific Characters: The skull, larger than that of M. cursor, is moderately low, broad, 

 and heavy, with the superior contour nearly straight, and is reminiscent of the general appearance of 

 Eporeodon in side view. The maximum expansion of the zygomata is just in advance of the glenoid 

 surface. The malar beneath the orbit is heavier than in M. cursor, and the zygomatic process of 

 the temporal, while long and slender, rises more abruptly than in the genoholotype. Its postero- 

 superior angle is curved inward and lies closer to the orbit than to the posterior termination of the 

 skull. The nasals are normal, narrowing very rapidly anteriorly from the narial opening and gradu- 

 ally aft, terminating more obtusely than in M. cursor. The lacrimal bone appears to be confined 

 mainly to the orbit. The lacrimal or antorbital fossa is large and deep, and there are no facial 

 vacuities. The frontals are wide and nearly flat. The orbits are medium in size and not situated so 

 high as in Pronomotherium. They are round in outline and look almost wholly sideward. The 

 temporal ridges join above the anterior of the glenoid surface to form a sharp sagittal crest that runs 

 about a third of the length of the skull and is moderately high. The supraoccipital crest overhangs, 

 but not so much as in M. cursor, and the wings are much more widely spread. The brain case is 

 about like that in Eporeodon, being somewhat less inflated than in the genoholotype. The external 

 auditory meatus is slightly more upwardly directed than in M. cursor. The palate is narrow and 

 concave, while the V-shaped palatonarial border begins nearly on a line with the end of the tooth 

 rows. The basicranial axis is moderately steep, and the glenoid surfaces are nearly flat. The post- 

 glenoid processes are stout but not long. The paroccipital processes are rather heavy, oval in cross 

 section, and apparently longer than in M. cursor. The bulla; are inflated and of medium size. 

 Index: 0.57. 



