lOxPLANATiox 01' Plate II 



Jtiw muscles of Amia and Lcpidosfeus, representing the Gauoidei Holostei, and 

 of Anguilla. representing tlie Teleostei Apodes 



Fi(is. 1 and 2. — Amia. (Muscles mainly after Allis.) 



In the Holostei and Teleostei the adductor mandibular and levator maxilhr? 

 superioris of selachians are subdivided into numerous muscles all lying in 

 front of the hyomandibular and innervated by Vg ; while the C. oSd. group 

 behind the liyomandibular, wliich is innervated by VII, includes three muscles 

 {Ad. hy.., A. o., L. o.). Tlie levator arcus palatini {L. a. p.) and the dilator 

 operculi (D. o.) belong to the C. iSd. series and api>ear to represent the pro- 

 tractor hyomandibularis of the sturgeon (PI. I, Fig. 3). The levator maxilhe 

 superioris (L.m.s.) includes several slips of which only one is shown. The 

 first division of the adductor mandibuke (Admi) covers the cheek behind the 

 eye and runs from the preoperculum to the mandible. The fourth division 

 (Adm^) is lodged in the Meckelian fossa of the mandible. The dilator opei-culi 

 (D.o.) passes through a groove or depression in the hyomandibular and is 

 inserted by tendon into the operculum. 



Fig. 3. — Lepidostcus. 



In correlation with the anteroposterior elongation of the head the jaw 

 muscles are nearly horizontal instead of vertical. This oblique insertion gives 

 great speed but low power in the closing of the jaw. The protractor hyomandib- 

 ularis {P. hy.), as in Acipcnscr (Plate I, Fig. 3), runs from behind the eye to 

 the anterior border of the hyomandibular. ,The second slip of the adductor is 

 now above the eye instead of behind it. 



Figs. 4 and 5. — Anguilla sp. 



In this peculiar teleost the adductor mandibulre is greatly enlarged and has 

 spread out upon the top of the skull after the fashion of the capiti-mandib- 

 ularis of certain, Amphibia. The large dilator (D.o.) and levator operculi 

 (L.o.) muscles assist in the strong respiratory movements of the branchial 

 region. 



