156 THE MERYCOIDODONTID^E 



found in direct association, but Peterson considered them as being of the same species of animal. 

 They were collected in the lower Miocene upper Harrison beds in Sioux County, Nebraska, not 

 many miles from the type locality of M. magnus. 



Peterson had the idea that these specimens might represent a new species and fully recognized 

 the important differences between the Carnegie material and the type of M. proprius. I believe that 

 this material represents the female of M. magnus, the type of which I consider to be a male. In 

 both specimens the anterior end of the nasal is above P 3 ; the position of the infraorbital foramen in 

 both is above the interval between M 1 and M 2 ; the position of the auditory meatus is the same; 

 the shape of the zygomatic arch is alike in both; the length of M 3 is less than the combined lengths 

 of M 1 and M 2 ; the superior contour of the skull, the antorbital fossa, the size, shape, and position 

 of the orbit, the sagittal and supraoccipital crests are all very similar in both specimens. The upper 

 and lower molar-premolar indices vary by exactly 0.02; the upper index is 0.78 in Peterson's speci- 

 men and 0.76 in M. magnus, and the lower is 0.72 and 0.70 respectively. The Peterson skull is 

 slenderer in build throughout. The zygomatic arches are lighter duplicates of the M . magnus type. 

 The skull is nearly as long as the latter but is slightly less wide than M. matthewi, giving an index 

 of 0.66, whereas in M. magnus it is 0.78 and in M. matthewi 0.73. 



Hence the skulls and jaws of both the type of M. magnus and the Carnegie specimens here 

 discussed closely resemble one another in all the major points of construction, and the latter vary 

 from the former in a type of build uniformly smaller and slenderer, which, as I stated above, 

 indicates the female of M. magnus. 



Merycochoerus matthewi Loomis 1924 

 PI. XXIII, figs. 4-5 



Original Reference: Miocene oreodonts in the American Museum. Bull. Amer. Mus. Nat. Hist., LI, 

 Art. 1, pp. 27-28, figs. 14-15. 



Type Locality: Three miles northeast of Porcupine Butte, South Dakota. 



Geologic Horizon: Lower Miocene (upper Rosebud). 



Type: Holotype, Cat. No. 12970, A.M.N.H., skull and jaws, united by matrix, with a good fore limb and 

 some other less perfect limb bones. Named in honor of the late Dr. W. D. Matthew. 



Specific Characters: The skull is smaller than that of M. magnus but is larger than that of 

 M. froprius, and it is much less shortened and is less broadened than either of those two. The 

 superior skull contour is nearly parallel to the line of the premolars, while in M. magnus, and still 

 more so in Al. proprius, there is a very decided slope forward from the sagittal crest. The depres- 

 sion near the roots of the nasal bones, so well developed in the other two species, is but slightly 

 marked in this species. The maximum expansion of the zygomata is near the posterior part of the 

 glenoid surfaces and is less than that of M . magnus. In side view the zygoma is nearly straight, 

 except for a posterior gentle upward curve, by no means attaining verticality. The malar is deep 

 beneath the orbit, but the squamosal portion is relatively weak. The nasals are short, posteriorly 

 obtuse, and of uniform width, with a convex upper surface. The infraorbital fossa is large and 

 deep. The frontals are wide and apparently extend in advance of the lacrimals, but the skull is so 

 thoroughly cracked that I cannot be sure of the exact position of some of the sutures. The frontal 

 bones are nearly flat, except for a small elevation near the junction of the nasal with these bones 

 between the orbits. The orbits are moderately small and look but slightly upward and forward. 

 The temporal ridges unite well aft, just anterior to the supraoccipital crest, and hence the sagittal 

 crest is very short and low. The small supraoccipital crest overhangs a short distance beyond the 

 occipital condyles, and the wings are widespread. The brain case is short anteroposteriorly and 

 moderately expanded, but not nearly so much as in M. magnus. The external auditory meatus is 

 relatively small, circular in cross section, upwardly and outwardly directed, and situated on a line 

 nearly as high as the upper end of the zygoma. The basicranial axis is shallow, and the palate is 



