1871.] HUIKE BEPXILIAN SKTJLL. 203 



under surface of the skull is bounded by a raised broken edge directed 

 downwards and backwards from the postorbital process towards the 

 basisphenoid. The middle of this edge is crossed by a deep, narrow, 

 horizontal groove continued forwards from a large foramen (v) situ- 

 ated nearly 1 inch behind. This groove may have lodged the ramus 

 ophthalmicus of the 5th cranial nerve. All that part of the broken 

 edge which is above and external to this groove is narrow ; it seems 

 to be the remains of the thin bony plate separating the orbit from 

 the temporal fossa ; while below and internal to the groove the edge 

 widens into a broad, rough, four-sided mass having mesially and 

 inferiorly the ascending basisphenoidal rod, in front the smooth under 

 surface of the orbito-sphenoid, above the narrow groove for the 

 ophthalmic branch of the 5th nerve, and behind a wide, shallow, 

 vertical groove which descends from the large foramen lately men- 

 tioned. This latter, from its great size and its position, can be none 

 other than the aperture which transmits the 5th nerve, the mandi- 

 bular division of which was probably lodged in the wide shallow 

 groove descending from it. That part of the side wall of the skuU 

 which lies in front of this foramen for the 5th nerve, behind the 

 orbito-sphenoid, and which below joins the basisphenoid, must con- 

 tain the alisphenoid. A narrow channel which ascends immediately 

 behind the wide shallow groove for the mandibular nerve from near 

 the posterior orifice of the carotid canal, and ends in a couple of 

 small foramina nearly at the level of the floor of the cranial cavity, is 

 probably arterial. One inch behind the foramen for the 5th nerve, 

 and at the same level, but separated from it by a buttress, is a de- 

 pression, at the bottom of which are two openings (fig. 1, vii). These 

 I take to be the auditory fenestrse ; and if this view be right, the part 

 of the side wall in front of them, and behind the foramen for the 

 5th nerve, contains the prootic bone ; while behind the auditory 

 fenestrge a buttress ascending from the basis cranii towards the lower 

 border of the suspensorium for the quadrate bone, in front of the ex- 

 occipital, has the relations of the opisthotie. In a triangular hollow 

 between this and the exoccipital are the foramina for the 8th and 9th 

 nerves (vin, ix). 



The side walls of the skull behind the foramen for the fifth nerve, 

 corresponding to the hinder half of the temporal fossa, slope outwards 

 more than in front; they project beyond the auditory fenestrse, which 

 they overhang, after the manner of the eaves of a house ; and be- 

 neath the overhanging eave, and nearly parallel with its outer border, 

 is a wide shallow groove produced from the hollow containing the 

 auditory fenestrse horizontally backwards and outwards to the root 

 of the suspensorial process, which probably lodged the stapes. 



The cranial cavity (fig. 2) is long and narrow. Its greatest trans- 

 verse measurement is in front ; and its maximum vertical one is at the 

 middle, nearly above the foramen for the fifth nerve. Two rather 

 broad constrictions divide it into three fossae. Of these the anterior 

 doubtless lodged the cerebral hemispheres ; it opens below into a 

 remarkably large hypophysial pit {lipf). The posterior wall of this 

 pit is vertical ; it makes a right angle with the floor of the cranial 



