JOXI'LANATION OF I'l.ATE All 



Jaw iiiusck'S uf slreptostylic reptiles: Iguaiid and Vanuius 



Figs. 1 and 2. — Iguana. (Muscles mainly aftei" Mivart. ) 



The superficial muscles are sliowu in Fig. 1, aud the deep muscles in Fiy;. 2. 



The capiti-mandibularis is divided into three layers, which have the same 

 arranii:emeut as in Sphciiodoii. The pterygoideus anterior {Pt. ant.) differs 

 from that of Alligator in hcing confined to the posterior part of the skull. 



Figs. o-.j. — ^'aranl(■^i. (Muscles mainly after Watkinson.) 



The superficial muscles are shown in Fig. 3, the middle layers in Fig. 4, 

 and the deep layers in Fig. 5. 



In correlation with the extreme mobility of the jaws the pterygoid muscles 

 are differentiated into four distinct elements, pterygoideus anterior {Pt.ant.), 

 pterygoideus posterior {Ft. post.), pterygo-sphenoidalis (Pt.s.), and pterygo- 

 parietalis {Pt.pa.). These are probaldy all derived from the primitive ad- 

 ductor mass and along with the three divisions of the capiti-mandibularis are 

 innervated by V,. 



