THE ELASMOBRANCH FISHES 



223 



Fig. 54 



A dissection of the ventral side of the throat of Scylliunt canicula, to show the 

 heart, cardiac aorta, and afferent branchial arteries. On the left side of the 

 figure the constrictor superficialis branchiarum muscle has been removed ; 

 biu the membranous gill-pouches have not been slit up, but have been pulled 

 outwards to exhibit better their relations to one another. On the right side 

 the gill-pouches have been slit up, and the gill-partitions and demi-branchs 

 have been cut away down to the level of the afferent branchial arteries. AB^- 

 AB~', the five afferent branchial arteries; CA, cardiac aorta; cf>r l -c/>>' 4 , the 

 cut ends of the first, second, third, and fourth coraco-branchiales muscles; 

 c/iy, cut end of the coraco-hyoideus muscle ; Cff, ceratohyal cartilage ; cm, 

 coraco-mandibularis muscle; e/>, inferior extra-branchial cartilage of the second 

 gill-arch ; Sl^, sinus venosus ; ///, thyroid gland ; V t ventricle. 



