. The Cambridge natural history. Zoology. 338 FISHES of the corresponding veins, the two genera exhibit a significant resemblance to the Dipnoi. In the Dipnoi the ventral aorta is so short that the afferent branchial arteries arise almost directly from the conus arteriosus with their roots in close contiguity to one another (Fig. 200). In Neoceratoclus (Fig. 200),-' there are two efferent vessels to each gill-bearing branchial arch, which unite above to form an epibranchial artery, and by the successive union of the four cl£Acl'. Fig. 200.—Branchial arterial
. The Cambridge natural history. Zoology. 338 FISHES of the corresponding veins, the two genera exhibit a significant resemblance to the Dipnoi. In the Dipnoi the ventral aorta is so short that the afferent branchial arteries arise almost directly from the conus arteriosus with their roots in close contiguity to one another (Fig. 200). In Neoceratoclus (Fig. 200),-' there are two efferent vessels to each gill-bearing branchial arch, which unite above to form an epibranchial artery, and by the successive union of the four cl£Acl'. Fig. 200.—Branchial arterial system of Neoceratodus. Lateral view. The comjs arteriosus and the afferent branchial vessels are represented in solid black, the efferent vessels and their derivatives with double contours, a, Auricle ; , anterior carotid ; , anterior cerebral artery ; ', first afferent branchial artery ; , brachial artery ; , coronary artery ; car, conus arteriosus ; , coeliaco- mesenteric ; , epibranchial artery ; , hypobranchial artery ; , hyoid artery ; , hyoidean arch ; , lingual ; , , left and right dorsal aortae ; oca, occipital artery ; , oesophageal artery ; p, pericardium ; , pulmonary artery ; , posterior carotid ; , posterior cerebral artery ; , sinus venosus ; v, ventricle ; 1, hyobranchial cleft; 2-5, branchial clefts. (After Baldwin Spencer, diagrammatic.) epibranchial arteries a short common trunk is formed on each side. Posteriorly, the two trunks unite to form a median dorsal aorta. Immediately above the gill-clefts each efferent vessel gives off a branch which, passing either forwards or back- wards, unites with the corresponding branch of the efferent vessel in front or behind as the case may be. A hyoidean artery arises from the ventral extremity of the anterior efferent artery of the first branchial arch, and, after giving off a lingual artery, ascends the hyoid arch and supplies the hyoide
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