MUSCULAR SYSTEM. 



115 



where the uniform character persists botli dorsally and ventrally, 

 retains throughout more primitive relations than does the ventral, 



FIG. 99. THE MUSCULATURE OF Siredon piscifarmis. (From the ventral side.) 



0, outermost layer of the external oblique, passing into the fascia, which is shown cut 

 through at F ; Oh, second layer of the same muscle ; Re, rectus abdominis, 

 passing into the visceral musculature (sternohyoid) at Re 1 , and into the pector- 

 alis major at P ; Mh, J\Ih l , anterior and posterior portions of the mylohyoid, 

 which is cut through in the middle line, and removed on the left side, so as to show 

 the proper visceral musculature ; Ce, Ci, Ci 1 , external and internal ceratohyoid : 

 the former is inserted on to the hyoid (Hy) ; Add, adductor arcuum branchialium ; 

 C, constrictor arcuum branchialium ; Oph, portion of the constrictor of the 

 pharynx arising from the posterior branchial arch ; Dp, depressores branchinrum ; 

 Gh, genio-hyoid : P/>, procoraco-humeralis ; Spc, supracoracoideus ; Cbb, coraco- 

 brachialis brevis ; Clo, cloaca ; La, linea alba. 



the latter becoming greatly modified in order to form the walls of 

 the body-cavity. 



I 2 



