] 030 MB. W. p. PrCBAFT ON THE [Dec. 19, 



sellae. This arrangement suggests an ossification of the basi- 

 sphenoid from three centres — a median longitudinal, running 

 forward to lodge the pituitaiy fossa, and two lateral wings. This 

 is a point for further investigation on fresh material. 



Tiie basisphenoid is bounded laterally by the alisphenoid, 

 postero-laterally by the procitic, and posteriorly by the basi- 

 occipital, and anteriorly by the presphenoid. 



The alisphenoid has partly fused with the orbital process of the 

 frontal, but is otherwise at present free. Externally it is roughly 

 circular in form. The posterior convex border follows the outline 

 of the concave anterior border of the squamosal, but the two 

 borders do not as yet even touch. Neither has the ossification of 

 its ventral border extended downwards as far as the parasphenoid. 



The orbito- and presphenoids have not as yet begun to ossify. 

 They are represented only in the dried skeleton by a thin trans- 

 parent sheet of tissue — the remains of the original cartilage. 



The mesethmoid is almost completely ossified and subcrescentie 

 in form, its convex border forwards. It extends vertically from 

 the parasphenoid below to the nasal above. 



The qvadrate has not yet assumed its fully adult form, the distal 

 end of the orbital process being only cartilaginous and relatively 

 shorter than in the adult. 



The columella is represented only by its base, which is ossified ; 

 the stapedial rays are not distinguishable in the dried skull. 



The articulare can still be distinguished as a separate element. 



b. Memhrane-bones. 



The panelal externally is oblong in form, with its borders 

 nearly straight and at right angles one with another. Immediately 

 above the antero-venlral angle of its anterior border it is over- ■ 

 lapped by a tongue-shaped process from the frontal. Its inferior 

 border rests upon the dorsal border of the squamosal, than which 

 it is a trifle broader. Its posterior or hinder border ventrad abuts 

 against the epiotic, which at this point is cartilaginous, and 

 dorsad forms a harmony suture with the supraoccipital. Internally 

 the angle formed by its hinder and ventral borders is cut off from 

 the inner surface of the skull by a portion of the pro- and epiotic 

 bones. 



The/»wz<a? has its hinder border nearly straight. Just above 

 its postero-ventral angle it sends backwards a slight linguiform 

 process to overlap the parietal. Its outer, ventral border caudud 

 extends downwards to within a short distance of the level of the 

 squamosal, cephalad it sends downwards a small orbital process to 

 overlap the alisphenoid. 



The squamosal seen externally is almost quadrate in form, but 

 widest along its dorsal border, which, like the remaining three, is 

 slightly hollowed. It articulates by a close harmony suture with 

 the parietal. In the hollow of its hinder border there is a small 

 osseous nodule representing a portion of the opisthotic. 



The squamosal is almost entirely excluded from the cranial 



