FELIS SPEL^A. 39 



however, it is easily separated from the basi- and pre-sphenoid, while the suture between 

 it and the pterygoid is obKterated at a very early age, we treat the alisphenoid and 

 the pterygoid as one bone for descriptive purposes. 



Nearly the whole of the outer surface of the bone is visible in the perfect skull, as 

 a vertical plate running upwards to form part of the walls of the cranium between the 

 temporal and optic fossae. It also extends horizontally as far back as the petrosal, passing 

 under the anterior part of the tympanic. Inferiorly, the pterygoids extend downwards and 

 backwards on either side of the great guttural groove, ending in the thin, strong, 

 hamular processes in lion and tiger, which in our spelaean skulls are unfortunately 

 broken away. Por purposes of description this compound bone may be divided into the 

 horizontal or guttural portion, the supero-vertical or temporo-optic, and the infero-vertical 

 or pterygoid portions. The first of these is a narrow plate, transversely concave, covering 

 the postero-lateral edges of the guttural surface of the presphenoid and the antero-lateral 

 edges of the basisphenoid. In the basisphenoidal suture is the orifice of the Vidian canal, 

 by which the nerve and artery of that name enter the alisphenoid, and pass forwards into 

 the orbit at the external border of the " foramen sphenoidale." We have ah-eady described 

 the groove connected with this canal on the surface of the basisphenoid in our account of 

 that bone (§ 4). The infero-vertical or pterygoidal processes curve downwards from the 

 horizontal portion, and articulate anteriorly with the palatine by a vertical suture. The 

 hamular processes, in which they terminate, are the equivalents of the internal pterygoid 

 plates of human anatomy, the externals being represented by a slight longitudinal ridge 

 immediately in front of the foramen sphenoidale. 



M. de Blainville^ states that the hamular processes of the tiger are less delicate than 

 those of the lion. The variations, however, in this respect, in both these species, do not 

 enable us to confirm this observation. As might be expected, these parts have not 

 occurred in a fossil state. 



The horizontal plate expands posteriorly behind the Vidian canal, and articulates with 

 the squamosal just within the boundary of " the glenoid cavity." At this point it joins 

 the supero-vertical or temporo-orbital process, which is a long, thin, triangular plate, 

 highly convex externally, articulating behind with, and passing under, the squamosal by a 

 highly concave suture, above with the antero-inferior angle of the parietal, in front with 

 the postero-inferior angle of the frontal, and the orbito-sphenoid. At the bottom of this 

 suture is a notch, which, together with a corresponding surface of the latter bone forms 

 the large " foramen sphenoidale,"^ to a certain extent the representative of the sphenoidal 

 fissure or " foramen lacerum anterius "^ in man, and giving passage to the third and 

 fourth nerves, to the first branch of the fifth pair, or the trigeminal, and to the sixth. 

 Immediately behind this, and rather lower down, is the foramen rotundum, for the trans- 



1 'Ost. Fclis,' p. 28. - Straus-Durckheim, op. cit., vol. i, p. 395. 



* Holder), ' Human Osteology.,' 3rd edit., p. 78. 



