906 THE OSTEOLOGY AND MYOLOGY OF THE DEATH ADDER, 



supplies the parieto-pterygoid. The inferior border rests on the 

 basisphenoid below. 



Os Orbitosphenoideum. 



Orhitosphenoidj Parker, Parker and Bettany, Hoffmann. 



The orbitosphenoid is a thin plate of bone only to be dis- 

 tinguished with difficulty from the surrounding bones. It lies on 

 the posterior and external portions of the lateral plate of the 

 frontal, and articulates with the orbital portion of the parietal. 

 It is reniform in outline, the concavity being anterior. The bone 

 helps to form the orbital fossa, and enters by a small process into 

 the formation of the optic foramen. 



Os Squamosum. 



Mastoideum, D' Alton, Harting, Joh. Miiller, Owen ; Squa- 

 mosum, Gegenbaur, Huxley, Parker, Parker and Bettany, 

 Wiedersheim, Hoffmann ; Schldfenschiqyi^e, Kallmann ; Zitzen- 

 knochen des Schlafbems, Meckel ; Tympanicum vel squamosum, 

 Rathke ; Squama teinjyoris, Stannius. 



The squamosal is prismatic in outline, and presents superior, 

 external, and internal faces. 



The superior face is slightly convex anteriorly, while posteriorly 

 it becomes narrow. The anterior portion gives origin to the 

 posterior temporal, while the posterior portion has part of the 

 digastric arising from it. 



The external surface is convex. The anterior half gives origin 

 to the posterior temporal ; the posterior half is articulated to the 

 quadrate by a convex facet. In Python it is the posterior 

 extremity of the bone that is modified for articulation with the 

 quadrate. The internal surface is broader anteriorly than pos- 

 teriorly; its anterior two-thirds is concave for articulation with the 

 convex facet in the epiotic. The posterior third projects backwards 

 and portion of the digastric is attached to it. The anterior 

 extremity abuts against the projection mentioned in connection 

 with the postero- lateral border of the parietal. 



