Cope.] 528 [Jan, 18, 
while the width exceeds both. The basioccipital bone is prominently 
keeled on the middle line, so that the section is a V of a more compressed. 
character than the section of the same in M. superbus. The median plane 
of the sphenoid is prominent, and is continued as a wedge with the apex 
opposite the posterior borders of the otic bull. The palatine borders are 
parallel, except where they form on each side ‘an open angle at the junc- 
tion of the descending process of the sphenoid, which is here directed for- 
wards. Its external border is distinct from that of the palatopterygoid 
plate, and makes a groove with it. The maxillary bone is not produced 
posterior to the notch on either side of the base of the posterior production 
of the palatine bones. The middle line of the latter is deeply concave 
opposite the former, and the palate is also especially concave between the 
first true molars. The palate is flat between the first and second pre- 
molars. The inferior surface of the squamosal process of the zygoma, is 
roughened for the origin of the masseter muscle. The inferior edge of the 
mular comes from its inner side, and is narrow and with a median groove. 
Its inferior edge is’ continued as a ridge of the maxillary as far as opposite 
the anterior lobe of the second true molar. The maxillary bones are more 
produced anteriorly than in any of the other species. The apex of the 
nasal bones stands above the posterior border of the canine in this species; 
above the anterior edge in M. superbus, M. chelydra and M. leidyt (fide 
Bettany). The posterior border of the nares is above the anterior part of 
the first premolar in the three species named, except M. chelydra wherevit 
is over the posterior edge of the canine: in I macrostegus it is above the 
posterior edge of the longer first premolar, 
The infraorbital foramen is large, and its posterior border is above’ the 
anterior root of the first true molar. The incisive foramina are large, and 
each one is a little longer than wide. The nareal opening contracts gradu- 
ally to its inferior apex. There is a considerable maxillary foramen op- 
posite the middle of the fourth superior premolars. The posterior nareal 
is not large; its anterior outline is regularly concave. Its lateral (sphe- 
noid) borders reach to opposite the anterior faces of the postglenoid pro: 
cesses and bound the foramen ovale on the inner side. The latter is round, 
is rather small, and is opposite the middle of the postglenoid surfaces. 
The foramen rotundum on the other hand is large and vertically oval, 
and is bounded below by a transverse prominence of the base of the ali- 
sphenoid bone. It probably includes the sphenodrbital foramen, a foramen 
anterior to its inferior border probably communicating with the nareal 
chamber. The optic foramen is small, and is situated opposite the ante- 
rior two-fifths of the zygomatic fossa and a little above the line of the 
apex of the foramen ovale, The foramen lacerum is ovoid and not large. 
The posterior foramen lacerum is a transverse sigmoid, one extremity 
being the jugular foramen.’ The mastoid and postpariétal foramina are 
of moderate and equal sizes. No postsquamosal or supra- or postglenoid 
foramina. 
The animal described is too old to exhibit sutures. 
