588 (Jan. 18, 
Jope.] 
posterior temporal crest, is as long as from the former point to the 
anterior base of the first premolar. In the Oreodon culbertsoni, the same 
measurement is equal to the length from the same point to the anterior 
base of the third incisor. This shortening posterior to the orbit is seen to 
involve the zygomatic fossa as well as the region posterior to it. Thus the 
horizontal diameter of the orbit in the M. leptorhynchus is exactly equal 
to the distance between the posterior border of the same and the anterior 
edge of the glenoid cavity. The posterior part of the superior edge of 
the squamosal zygomatic process is thin and strongly convex. The apex 
of the convexity is above a point just anterior to the posterior border of 
the glenoid cavity, The posterior edge of the process is nearly vertical, 
and if continued would reach the middle of the base of the postglenoid 
process. The latter is compressed and rather elongate, and its convex 
edge has considerable transverse extent. The paroccipital process is long 
and is flat on its posterior face. The postorbital process of the frontal is 
clongate wedge-shaped, with its truncate apex below joining a slight ele- 
vation of the malar bone, which is much less prominent than in Oreodon 
culbertsoni. It presents an angle outwards and forwards, as the orbital 
border, The anterior half of the zygomatic process of the malar bone is 
rounded.truncate below. The glenoid surface is plane transversely, and 
slightly convex, rising backwards, anteroposteriorly. The anterior border 
of the squamosal bone is not developed into a ridge. 
The frontal bone extends forwards on either side of the nasals, forming 
a narrow process above the lachrymal bones. It overlaps the superior 
edge of the maxillary, of which a narrow splint appears between it and 
the nasal. The nasals are rather narrow, and each has the posterior bor- 
der rounded. The latter fall above the middle of the first true molar 
tooth when the inferior edge of the mandible is horizontal. The lachry- 
mal bone has greater anteroposterior than vertical diameter, extending 
nearly to the line of the infraorbital foramen, or much in advance of its 
position in Oreodon culbertsoni, Hucrotaphus jacksoni, or Merycocharus 
superbus. The malar bone has a correspondin ely large anterior extension, 
reaching to above the posterior part of the fourth premolar. It does not 
extend so far in the three species just named. The zygomatic process of 
the squamosal is more deeply received into the malar bone than in any of 
the three species mentioned, reaching to below the posterior third of the 
orbit. 
The larmier in this species is small, and its anteroposterior diameter is 
more than twice as long as the vertical. More than half of its inferior bor- 
der is formed by the maxillary bone. As it is exhibited in the specimen, 
its superior border is formed by the ascending process of the maxillary 
bone; whether this is overlapped by the laminar process of the frontal so 
as to bound the foramen, when in a perfect condition, is uncertain. The 
posterior edge of the larmier is the lachrymal bone. ‘The external foramen 
infraorbitale is on one side double. The supraorbital foramina form 
notches at the anterior edge of the supraorbital border. The frontal 
