Basioccipital, exoccipitals, and super- '^ 



occipital, • I forming the walls 



Basisphenoid and presphenoid, all- [of the skull. 



sphenoids, ^ j 



Mastoids, 1.* 



Parietal, 2. 



Frontals, 3, postfrontals, 4, prefrontals and lacrymals, 5. 



Vomer, nasals, 6, and turbinals t. 



The maxillary arch is composed of the following bones : — 



The premaxillary, 7, a small bone wedged in the nasal 

 interspace and, except in the Pythonidce, not bearing teeth. 



The tnaxillaries, 8, one on each side, of very variable 

 shape. 



The palatines, 9, otie on each side, .lie parallel to the 

 maxillaries between them ; they bear teeth except in 

 Oligodon and some earth snakes. 



The pterygoid, 10, and ectopterygoid, 11, of each side form 

 a KJ shaped bone (the ectopterygoid being represented 

 by the thin stroke) they abut against the posterior 

 extremities of the palatine and maxillary respectively, com- 

 municating motion to them. The pterygoid bears teeth 

 continuously with the palatine row; its posterior end is 

 loosely connected with the tympano-mandibular joint. 



The mandibular arch comprises the following : 



The mandibles or lower jaw bones, 12, connected at the 

 chin by the geneial muscles and skin only. Each mandible 

 is composed of two principal parts, the articular posteriorly 

 and the dentary in front ; these are connected by a wedge- 

 shaped suture at the back of the row of teeth. The articular 



* The figures refer to Plate I, figs. 1 and 2. 



