188 THE MERYCOIDODONTTEVE 



fossa. The anterior narial opening is large and broad and situated rather far back. The nasal bones 

 are broad at the anterior junction with the maxillaries, but they narrow rapidly posteriorly and end 

 in a blunt point just above the antorbital margins. This produces an appearance somewhat like that 

 in Merycochcerus, but the species is not referable to that genus. The orbits are rather large and 

 are situated well up on the side of the skull. 



Mandible: The symphysis forms an angle of 50° with the tooth row, and it is concave verti- 

 cally and convex transversely, with a prominent angle at its inferior termination. The ascending 

 ramus is deep, vertical posteriorly, and moderately broad. The masseteric fossa is deep but not 

 extensive, while the coronoid process is short and stocky. The sigmoid notch is wide open and 

 descends but slightly below the condyle, which is nearly flat superiorly, falling off rapidly 

 posteriorly. The angle has more prominence than is usual in this genus. The horizontal ramus 

 increases in depth from beneath P 3 to the beginning of the angle below the middle of M 3 . 



Dentition: The inferior teeth are hypsodont, with the premolars crowded and overlapping and 

 with cingula on the outer faces of the molars. The last lobe of M n is unusually small, with its axis 

 trending outward, as in T. hypsodus. In the other species this lobe is of more nearly equal size with 

 the two preceding ones of M 3 and is much more in line with them. The apices of P2, P3, and P 4 

 are almost centrally located. Lower molar-premolar index, 0.73. 



Skeleton: "Compared with other species the limbs are intermediate in length, fairly robust. 

 The cuboid is unusually high for its width." (Douglass.) 



Ticholeptus brachymelis Douglass 1907 

 Fig. 138; PI. XXIX, figs. 3-4 



Original Reference: New merycoidodonts from the Miocene of Montana. Bull. Amer. Mus. Nat. 

 Hist., XXIII, Art. 32, pp. 809, 815-817, 822, figs. 6, 7. 



Type Locality: East side of the North Boulder River, opposite Cold Spring Post Office, Montana. 



Geologic Horizon: Upper Miocene (Deep River). Type found in the same beds as Mcrycoides (Meso- 

 reodon) lo?igicefs Douglass, which see. 



Type: Holotype, Cat. No. 9731 A.M.N.H., comprises "a nearly complete skull with the mandible, the 

 cervical and lumbar vertebra:, nine or ten dorsal vertebra? part of which are incomplete, and the greater portions 

 of the fore limbs." Collected by Albert Thomson in 1902. The skull and jaws have not been separated. 



Specific Characters: The facial part of the skull is deep. In size it is closest to T. petersoni 

 and is more mesocephalic than T. breviceps. The superior contour of the skull is nearly straight. 

 The zygomata are not widely expanded, and their maximum is in advance of the glenoid. They do 

 not arise abruptly in front of the orbit, as they do in T. zygomaticus and, to a lesser degree, in 

 T. breviceps. The malar is very deep below the orbit, but the squamosal part of the zygoma is 

 weak in proportion and turns upward abruptly above the glenoid surface. The exact definition of 

 the facial vacuities cannot be made out with certainty. These vacuities were apparently moderately 

 large and bounded by the usual bones. I suspect that they appear to be larger than they actually 

 were, because the bone of the deep lacrimal pit has been so damaged that it apparently makes two 

 confluent vacuities where but one, the anterior, was normal in life. The nasals are shortened and 

 pointed posteriorly. They are very gently convex in both directions. The premaxillaries are 

 coossified for 12 mm. of their distance. The lacrimal bone cannot be clearly defined but was spread 

 in advance of the orbit to some extent, in all probability, and carried a deep pit. The frontals are 

 not wide but are fairly flat transversely, except over the orbits, and they extend in advance of the 

 lacrimal. The orbits are small and round and in the usual position for this genus. The temporal 

 ridges unite just above the anterior edge of the glenoid surface to form a short, rather low sagittal 

 crest. The supraoccipital crest extends slightly beyond the posterior line of the occipital condyles, 

 and the wings were spread apart. The brain case is low but proportionally wide. The external 



