226 



COMPARATIVE ANATOMY 



sea 



d ao 



Fig. 55 



A. dissection of the roof of the pharynx of Scyllium canicuia to show the efferent 

 branchial arteries and their relation to the gill-slits. The mandible, hyoid, and 

 branchial cartilages have been cut through on the animal's right side, and the 

 floor of the phnrynx has been forced over to the (animal's) left. The floor of 

 the cranium and the left orbit has been removed to show the course of the 

 carotid arteries. 1-5, the five gill-slits, the first four surrounded by the loops of 

 the collecting vessels, but the fifth has only a half loop on its anterior margin ; 

 I-IV> the four efferent branchial arteries; />r l -/>r r> , the five branchial arches; 

 cca, common carotid artery ; ca\a, the coeliac artery ; d.ao, dorsal aorta ; DC, 

 ductus Cuvieri ; eca, external carotid artery ; H.A, hyotdean artery ; ky, hyoid 

 arch ; tea, internal carotid artery ; nrd, mandible ; P, cut end of pectoral 

 girdle; sea, subclavian artery; sf, internal opening of spiracle ; S.V, sinus 



