THE ELASMOBRANCH FISHES 



223 



I-'ig- 54 



A dissection of the ventral side of the throat of ScyU'mm canicula, to_ show the 

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

 figure the constrictor superficialis hranchiarum muscle has been removed ; 

 but 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; cbr^-cbr^, the 

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

 chy, cut end of the coraco-hyoideus muscle ; CH, ceratohyal cartilage ; c?«, 

 coraco-mandibularis muscle ; el>y inferior extra-branchial cartilage of the second 

 gill-arch ; SV, sinus venosus ; ih, thyroid gland ; F, ventricle. 



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