115 



where the uniform character persists both dorsally and ventrally, 

 retains throughout more primitive relations than does the ventral, 



FIG. 99. THE MrscuLAn/KE or Siredm puetfomis. (From the ventral side. ) 



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

 through at F ; Ob, second layer of the same muscle ; Be, rectus abdominis, 

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

 alis major at P ; Mh, JIh 1 , 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 (By) ; Add, adductor arcunni branchialium ; 

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

 pharynx arising from the posterior branchial arch ; Dp, depressores branch iarum ; 

 Gh, genio-hyoid : Ph, 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 



