Cope.] 64 [Feb. 17, 
of the premaxillary bone. It contains the posterior four molars, with the 
alveole of the anterior three premolars and the canine of the left side. 
The specimen belongs to the collection of Prof. Thomas Condon, of the 
University of Oregon, who kindly lent it to me. 
The skull is remarkable for the abrupt contraction of its outlines ante- 
rior to the orbits, both laterally and vertically, The frontal region above 
and anterior to each orbit is swollen, indicating large sinuses. The ante- 
rior orbital border is notched twice, the superior emargination being rather 
shallow, while the inferior projects in an angle forwards, and the lachry- 
mal foramen enters at its apex, just within the facial border. The muzzle 
is contracted, compressed, and short. The zygomatic arch springs 
abruptly, its external surface meeting the everted facial surface in an ob- 
tuse vertical angle. This angle is opposite the anterior edge of the second 
true molar. Its posterior base is opposite the second pair of cusps of the ;3 
third true molar. The external face of the maxillary bone is directed in- 
wards and backwards from this point, and forms a vertical angle opposite 
the internal margin of the last molar. Its internal border, commencing at 
this angle, extends forwards, but I cannot in the specimen distinguish it 
from the adjacent parts of the palatine bone, on account of its injured 
state. The palate is flat except next the molars, where its surface is re- 
curved. The frontal region is flat, except at the superciliary borders, 
where it is slightly decurved. 
The nasal bones are narrow, but they expand posteriorly so as to have a 
width three times as great as at the middle of the length. The posterior 
outline of both is a single convexity, whose middle point is at the line 
connecting the anterior border of the orbits. The length of contact of the 
nasal with the maxillary bones is 12 to 15mm. The lachrymal bone is 
| higher than long, and wider above than below. Its anterior suture is 
nearly straight. The anterior part of the malar is deeper than the lachry- : 
| mal, and its anterior suture is concave posteriorly. 
The lachrymal foramen is single and round. The infraorbital foramen 
| is vertical and is above the posterior border of. the first premolar. The 
i 
incisive foramina are large. The supraorbital foramina are close together, 
being separated by an interspace equal one-fourth that which separates | 
each from the superciliary border. The grooves which extend from them | 
anteriorly diverge gradually and are lost near the apices of the premaxil- | 
lary bones. The palatine foramen is opposite the line of contact between 
the first and second true molars. 
The dental series is remarkable for the rapid diminution of dimensions of 
the teeth from behind forwards. The last molar is fully equal in size to the 
corresponding tooth in the Bothrolabis pristinus, but the first true molar and 
first premolar are very much smaller than in that species. The same rela- 
tion exists between this species and the BS. subequans. In comparison with 
the B. trichenus, the anterior teeth are smaller, while the last true molar is 
larger, in the @. decedens. The crowns of the molars are of simple con- 
stitution, They consist of four cusps, two external and two internal, the 
