Explanation of Plate III. 



Jaw muscles of Esox, representing the Teleostei Haplomi, and of 

 Palinurichthys, representing the Teleostei Acanthopterygii 



Figs. 1 and 2. — Esox. (Muscles mainly after Vetter.) 



The superficial muscles are shown in Fig. 1, and the deep muscles in Fig. 2. 



In this rather primitive teleost the divisions of the adductor are substan- 

 tially the same as in Amia (PI. II, Figs. 1,2). The protractor hyomandibu- 

 laris is either absent or not separate from the levator arcus palatini (L. a. p.). 

 The fourth branch of the adductor fills the Meckelian fossa of the mandible. 

 The dilator operculi (D.o.) passes above the hyomandibular and the pre- 

 operculum in the normal manner. 



Figs. 3-5. — Palinurichthys. (Identification of muscles after Vetter in Perca.) 

 These are the jaw muscles of a highly evolved teleost. The protractor 

 hyomandibnlaris (P. hy.) is distinct from the well developed levator arcus 

 palatini (L.a.p.). The retractor hyomandibularis (R.hy.), the levator oper- 

 culi (L.o.) and the so-called trapezius of the pectoral girdle are extended for- 

 ward above the orbit, on either side of the sagittal crest. 



