the 57cu/^/Diaden.o(lon. 301 



skull, and also appears as a small arrow-head-sliaped bone at 

 the extreme back of the parietal ridge in a dorsal view of the 

 skull (fig. 1). 



The two parietals appear to remain distinct in the skull 

 under consideration ; they unite in a sagittal suture along 

 the posterior half of the parietal crest which separates the 

 great temporal fossae ; anteriorly they separate A^ery slightly 

 and form the pineal foramen ; it appears probable that their 

 anterior ends Avere separated by very narrow laminse of the 

 frontals, and terndnated some 3 or 4 millimetres in advance 

 of the foramen, but this is not quite certain (fig. 1). 



For about 1 centimetre behind the pineal foramen the 

 parietal is supported on its outer face by a very thin and 

 quite shallow splint of postfrontal (lig. 5). 



The parietal in this region is a gently curved plate of bone 

 falling down on the side of the brain-cavity until it meets 

 the xipper border of the columella cranii in a very long 

 suture ; it appears to be certain that this union extends 

 forwards quite to the back of the orbit, passing forwards 

 well underneath the frontal. Along or just above the junc- 

 tion of the parietal and columella lies a deep well-rounded 

 groove, the anterior part of which is, when perfectly pre- 

 served, covered by a thin lamina descending from the 

 parietals. At a point about 1 cm. behind the pineal foramen 

 this groove receives a large oval and backwardly directed 

 foramen, which must lead into the brain-cavity ; this fora- 

 men appears to be bounded below by the columella and 

 pro-otic. Behind this region the parietal is formed by a 

 very thin, almost flat plate which passes ovitward and back- 

 ward. The upper part of this plate is supported behind by 

 the interparietal; lower down it is freely exposed on the 

 posterior surface of the skull and is united by suture Avith 

 the supra- and exoccipitals ; it forms the upper border of 

 the small post-temporal fossa, and sends down a thin flange 

 outside the fossa in contact with the distal end of the par- 

 occipital process (fig. 4). 



On the outer face this plate is overlapped by a thin process 

 of the squamosal which runs forwards to within 1^ cm. of 

 the junction of the sagittal and coronary crests. On its 

 anterior face this plate is seen to unite with the pro-otic part 

 of the periotic as far back as the post-temporal fossa ; along 

 this junction it bears a deep rounded groove, continuing that 

 found further forwards ; this groove opens into the post- 

 temporal fossa (fig. 5). The free edge of the parietal along 

 the sagittal and coronary crests is marked with small muscle 



