﻿TELIS SPELtEA. 41 



In the smaller Taunton skull this bone is nearly perfect, and as the palate is broken 

 away the anterior portion is visible. We are consequently able to describe all the free 

 surfaces of the bone. 



The visible portion of the inferior surface is a narrow strip, widening slightly pos- 

 teriorly and considerably anteriorly, which forms the central portion of the roof of the 

 posterior nares. The posterior portion is covered by a deep overlap of the pterygoid, 

 and the anterior by a similar overlap of the palatine. The posterior end is firmly 

 anchylosed to the basisphenoid by a deep suture convex posteriorly. These sutures are 

 indicated in PL VIII, No. 9, by faint lines, as they are nearly obliterated in the skull by 

 age. This surface is nearly flat in Felis spelaa ; this is also the case in the majority of 

 the lions' skulls that we have met with ; whereas in the majority, if not all of the tigers' 

 skulls, as well as in most of the other Eeles, there is a strong longitudinal central ridge, 

 which receives on each side of it the prolonged posterior processes of the vomer. 

 Anteriorly the bone is seen to consist of a thickened central mass, which rises into a thin 

 vertical plate, separating the ethmoidal sinuses, and articulating firmly with the central 

 plate of the ethmoid, a portion of this articulation is seen in the skull we are 

 describing. The central mass expands laterally into two thin plates, covered by the 

 overlap of the palatine before mentioned, which form the floor of the ethmoidal sinuses, 

 for the reception of the infra-lateral processes of the ethmoid, sometimes called the 

 " cornets de Bertin." 



The outer walls of these sinuses are formed by thin plates rising from the outer edges 

 of the floor, at first inclining somewhat inwards, and covered by the overlap of the vertical 

 plates of the palatine, but posteriorly these are uncovered, and arch over outwardly and 

 form the lower and posterior surface of the orbit. This free portion is pierced on each 

 side near the centre by the large optic foramina, which pass backwards and downwards to 

 the optic groove on the cerebral surface of the bone ; the lower part of this surface is 

 traversed by a strong ridge, below which the bone is roughened for the insertion of the 

 powerful Fallopian muscle for raising the lower jaw. 



The roof of the ethmoidal sinuses is formed by a thick plate, narrow horizontally and 

 anteriorly, but widening much posteriorly, at the same time curving downwards, so that 

 it unites with the much thickened posterior end of the central mass at its junction with 

 the presphenoid, forming at this point the homologue of the olivary process in man. 

 Above, in front of this is the very deep transverse optic groove, the ends of which lead 

 outwards, as before stated, to the optic foramina. The anterior portion of this, the 

 cerebral surface of the bone, is the floor of the rhinencephalic fossa, the walls and roof of 

 which are formed by the frontals. Anteriorly this surface rises centrally into a strong 

 vertical ethmoidal spine, to which is anchylosed the cribriform plate, for the lower foramina 

 of which the anterior edge of the orbito-sphenoid is deeply furrowed. The anterior edge 

 of the vertical walls of the ethmoidal sinuses is articulated to the vertical walls of 

 the palatine by firm sutures inclining forwards, to the frontals by nearly horizontal 



