324 PROFESSOR OWEN ON THE SKELETON 



is divided into an anterior (PI. LI. fig. 1, n) and posterior (ib. t) compartment ; the 

 latter divisions meet above and define a short low " parietal " ridge (ib. fig. 2,7). 



The fore or postorbital part of the temporal fossa is divided from the deeper back 

 part by a low ridge descending from the hind angle of the smooth convex frontal tract 

 to the fore part of the mastoid. The interorbital supracranial space is occupied by the 

 deep oblong fossae (ib. so) of the superorbital glands, between which fossae is a sharp 

 median ridge. A lateral ridge defines each fossa from the superorbital ridge itself, which 

 is very narrow. There is an oval vacuity for the duct of the gland at the outer and fore 

 part of each superorbital fossa, 4 lines, by 2 lines in diameter ; and there are two or three 

 foramina at the back part of each fossa, leading to the orbit. The postorbital process (12) 

 is depressed and triangular, impressed above by the fore part of the temporal fossa, which 

 is there divided by a short longitudinal ridge from the superorbital glandular fossa. 



The prefrontals (ib. fig. 1, n) send outward a triangular antorbital plate, which inclines 

 a little forward to join the lacrymal, but leaving an intermediate lacrymal vacuity about 

 the same size as that for the duct of the superorbital gland. 



The basisphenoid rapidly narrows as it advances forward, and does not send out pro- 

 cesses (pterapophyses) for the tympanic or pterygoid bones ; its presphenoid prolongation 

 (ib. fig. 3,9) diminishes in transverse but increases in vertical extent, developing upward 

 the lower part of the interorbital ridge, which is continuous with the ossified anterior 

 part of the interorbital septum, and, by means of its backward extension, with the orbito- 

 sphenoids (ib. 10). The lower border of the presphenoid is convex, and rests upon the 

 groove formed by the approximated palatines (20) and intervening vomer (13). 



The very thin fore part of the cranial wall shows four large vacuities, one medial 

 and superior, triangular, and giving exit to the crura of the olfactory lobes, which 

 slightly groove the under surface of the interorbital part of the frontals on their way to 

 the prefrontals. On each side and a little below the olfactory aperture is an irregular 

 oblong vacuity. An ossified tract of the interorbital septum extends from the confluent 

 orbitosphenoids, between the above vacuities and below the olfactory one, forward to 

 the anterior ossified part of the septum : a narrow unossified tract lies above, and a 

 broader unossified oblong space is beneath this upper ossified part of the septum. The 

 inferior vacuity gives exit to the optic and orbital nerves. 



The palatines (ib. fig. 3, 20) are broadest behind, and present each towards the palate a 

 long triangular surface sloping from within outward and downward, and defined mesially 

 by a low vertical plate bounding an angular cavity thus formed on that surface. The 

 narrower anterior prolongations of the palatines are confluent with the palatal processes 

 of the maxillaries (ib. 21), near to which they also develope from their inner border a low 

 vertical ridge. The upper surface of each palatal, near its middle part, developes the 

 curved outer wall of the posterior nostril, which is convex externally ; the palatal termi- 

 nations of these nostrils are longer and narrower, and are divided by the compressed 

 elongate vomer (is). 



