ARTERIES 453 



close together, and supply the gills on the third and fourth 

 branchial arches respectively : it will be remembered that 

 the fifth branchial arch bears no gill-filaments. After 

 aeration the blood from each hemibranch passes into an 

 efferent branchial artery (ef. br), which joins with its fellow 

 of the same cleft (except in the case of ef. br 9 ), and thus 

 forms a loop surrounding the cleft, the two halves of adjacent 



FIG. 121. Diagram of the heart and branchial arteries (of one side only) of 



Scyllium ; lateral view, (x i.) 



af. br. l- 5 , afferent branchial arteries ; au. auricle ; c. a. conus arteriosus ; d. 1 - 5 , 

 branchial clefts ; cor. coronary artery ; d. ao. dorsal aorta ; d. c. dorsal carotid 

 artery ; ef. br. 1 -9, efferent branchial arteries ; ep. br. !- 4 , epibranchial arteries ; 

 mn. mandibular artery ; sp. spiracle ; s. d. subclavian artery ; s. v. sinus 

 venosus ; v. ventricle ; v . ao. ventral aorta ; v. c. ventral carotid artery. 



loops being connected in the middle by a commissural 

 vessel. From, the upper ends of each of the four loops arises 

 an epibranchial artery (ep. br} which is connected with the 

 dorsal aorta (d. ao), the blood from the last hemibranch 

 passing into the fourth loop. 



From the dorsal end of the first efferent branchial, a dorsal 

 carotid artery (d. c) is given off ; this passes forwards and 

 inwards, gives off a branch to the upper jaw and snout, and 

 then runs inwards in a groove on the skull-floor, which it 

 penetrates in the middle line so as to reach the cranial 

 cavity. A vessel arises from the middle of the first efferent 

 branchial and supplies the pseudobranch, and is then 

 continued into a ventral carotid artery (v. c), which passes 

 through the orbit into the cranium, giving off branches to 

 the brain and anastomosing with the dorsal carotid. From 



