ON THE 
FORAMINA PERFORATING THE POSTERIOR PART 
OF THE 
SQUAMOSAL BONE OF THE MAMMALIA. 
BY B.D. COPE. 
The number of perforations of the posterior part of the squamosal bone 
in the Mammatia is considerable, and they have not attracted that atten- 
tion from anatomists which their importance deserves. As I have found 
them to be especially valuable in diagnosis, I have thought it might be 
useful to place on record the manner of their occurrence in various re- 
cent genera with whose structure we are more or Jess familiar in other 
respects. 
The one of these foramina of which some notice has been taken, is the 
postglenoid, which is mentioned by Flower (Osteology of Mammalia) as 
occurring in the dog and bear, and as absent in the cat. I find five other 
foramina which usually form the outlets of canals which are connected 
with the lateral venous sinus. The principal canal extends from the post- 
glenoid foramen upwards and backwards between the os petrosum and the 
squamosal, and enters the cranial cavity at the superior border of the for- 
mer. Ata point in the parietal bone, often on or very near the squamoso- 
parietal suture, it issues on the surface again, in the foramen which may be 
called the postparietal. A branch of the canal may take a posterior direc- 
tion and issue on the occipital face of the skull in the suture between the 
ossa petrosum and evoccipitale, forming the mastoid foramen. Or a pos- 
terior branch may issue in the posterior part of the squamosal bone in a 
lateral foramen, the postsquamosal. In certain Mammals a large foramen 
perforates the base of the zygomatic process of the squamosal from above, 
entering the canal after a short course of its own; this I call the supra- 
glenoid foramen. Still another inlet to the canal is found in some Mam. 
mals, perforating the squamosal below the crest which connects the zygoma 
with the inion, occupying a position posterior and exterior to the post- 
glenoid, and generally looking more downwards than outwards. I call this 
the sudsquamosal. These foramina may be arranged in four sets, as follows : 
I. Looking downwards ; 
Posiglenoid. 
Subsquamosal. 
II. Looking outwards ; 
Postsquamosal. 
‘Postparietal. 
III. Looking upwards ; 
Supraglenoid. 
IV. Looking backwards ; 
Mastoid. 
