ADAMS, PHYLOGENY OF THE JAW MUSCLES 85 



ping the other muscles of that region. It is double-headed, arising on the 

 posterior upper limb of the squamosal and from the lower part of the 

 annulus tympanicus and from the dorsal fascia. The anterior head arises 

 on the posterior limb of the squamosal and from the lower part of the 

 tympanic annulus. It joins with the posterior portion and is inserted on 

 the angular. The head tliat arises on the dorsal fascia springs from the 

 region of the upper part of the scapula and extends down to join the 

 anterior or cephalic portion of the muscle. The anterior head tightens 

 the ear-drum and lowers the jaw. 



CRYPTOBRANCHUS 

 Plate V, Figs. 3, 4 



The skull of Cryptobranchus (using this name in a broad sense to 

 include the American and Japanese forms) is much depressed and 

 widened. The squamosal is far up on the skull, making a shoulder and 

 groove around which the temporal muscles ride, so that their path is 

 well fixed. The pterygoids are flattened out to fill the region posterior 

 to the palate and to supply good origins for the muscles. 



MUSCLES OF THE ADDUCTOR OR TEMPORAL GROUP 

 {INNERVATED BY V^) 



Capiti-mandibularis superficialis (C. m. s.). 



= Masseter (Osawa). 



= Petro-tympanicus (Hoffmann) . 

 Capiti-mandibularis profundus (C. m. p.). 



^ "Temporalis" (Osawa) . 

 Pterygoideus posterior. 



= Pterygoideus (Hoffmann and Osawa). 

 Pterygoideus anterior. 



= Temporalis of Osawa. 



= Fronto-parieto-maxillaris of Hoffmann. 



MUSCLES OF THE DEPRESSOR OR DIGASTRIC GROUP 

 (INNERVATED BY VII) 



Depressor mandibuls (D. m.^, D. m.^). 

 = Digastric of Humphrey. 

 = Cephalo-dorso-maxillaris of Hoffmann. 



