SKELETON OF PKOBOSCIDIA. 



439 



details: — The basioccipital is uotclied behind, and contributes 

 there the lower ends of the occipital condyles : it increases in 

 thickness as it advances to form the liat rough surface for 

 junction with the centrum in advance (basisphenoid). There is a 

 rough depression on each side of the under surface for the inser- 

 tion of the ' recti capitis antici.' The exoccipitals form small, 

 inferiorly approximate condyles, fig. 295, 2, have no precondyloid 

 foramina, and do not develope paroccipital processes : they meet 

 above to complete the foramen magnum. The superoccipital is 

 much expanded, and supports two supplementary bones (inter- 

 parietals) : it is deeply impressed by the insertion of the liga- 



295 



296 



mentum nuch*. The basisphenoid has coalesced with the ali- 

 sphenoids. which are separated from their neural spine (pariet- 

 als, :) by the intercalated squamosals, g. The pterygoid processes 

 ai'e long, much expanded and excavated anteriorly, and are per- 

 forated at their base. The alisphenoids are perforated by a wide 

 * foramen ovale." The basisphenoid when united with the pre- 

 sphenoid receives air into the cells with which the bone, as it 

 acquu'es vertical extent, is excavated. The vomer retains its 

 character as a vertical plate, fig. 296, 13. The orbitosphenoids 

 have coalesced with each other at their base, and also vrixh the 

 prefrontals (laminae media? »thmoidei) : they are perforated by the 

 optic foramina, and notched posteriorly for the foramen rotundum. 



