Explanation of Plate III. 



Jaw muscles of IJso.v, representing the Teleostei Hiiplomi, anil of 

 roHnurirhthi/s, representing the Teleostei Acanthopterygii 



Figs. 1 and 2. — Eso.r. (Muscles mainly after Yetter.) 



The .superficial muscles are shown in Fig. 1, and the deep mu.scles 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). Tlie 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. oj passes above the hyomandibular and the pre- 

 operculum in the normal manner. 



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

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

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

 palatini {L.a.p.). The retractor hyomandibularis (R.liii.), 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. 



