20 UAMMALIA. 



0' 85 long, and still another on the posterior portion of the 

 parietal close to tlfe posterior end of the left temporal ridge. 

 There is no trace of a sagittal suture. Nearly opposite to the 

 first depression on the parietal, but immediately external to 

 the left temporal ridge, there is another and sixth depression 

 which seems to make itself felt along the inner side of the left 

 temporal ridge. On making two transverse sections through 

 these depressions and the intervening elevations, it is found 

 that in the last of the depressions there is considerable thin- 

 ning away of the walls of the skull, the cancellated substance 

 having disappeared, and nothing but the hard tables remaining, 

 in some places not thicker than C'DS ; so that, had the thin- 

 ning been carried a little further, the skull might have presented 

 the anomalous appearance of a series of openings in deep 

 depressions.' In such instances the depression is fully O'-IO 

 in depth, and the walls of the skull on either side of it are 

 fully O'-20 thick, with the diploe well developed. Between 

 the depressions of either side is an elevated, but flattened, area, 

 occupying the middle of the frontal. On the inner surface of 

 the skull there are no concavities corresponding to the external 

 •depressions, but there is one small circular pit about C'SO 

 in diameter underlying the thickened area on the frontal. 

 These defects in the skuU appear to be due to an imperfection 

 in the ossifying process, as stated by Professor Humphry, 

 in consequence of which those parts of the skull are left 

 thin. 



It will be observed that these depressions, as in the in- 

 stances cited by Professor Humphry in Man and in the Orang, 

 do not occur in the course of the sagittal suture nor on the 

 eminences of the frontal.^ 



Finding these depressions, in the two instances recorded, 



1 The stull of a female New Hollander in this Musenm has one great 

 parietal depression on the left side of the same natnre as those in the Orang 

 described above, another but smaller depression on the right side, and abont 

 six other irregular depressions on the left side. The first-mentioned depres- 

 sion is thinned away at its bottom to 0"'03. 



3 In the foregoing New Holland skull the largest of the left parietal 

 depressions involves the left parietal eminence. 



In the Museum of the Medical College the sknll of a young female Orang 

 ' presents a simple depression on the commencement of the sagittal suture, and 

 another slight one 0"'70 by 0"'50, which has its outline well defined by a 

 clear difference in the texture of the depression and that of the surrounding 

 parts. The depressed area is very dense and almost porcelaneous. This 

 skull also presents two deep pits on either side of the foramen magnum. 

 The lambdoidal and sagittal sutures are obliterated, but the skull is very 

 ' small, although it has got its lower permanent and its middle upper 

 incisors. 



