[Illustration: FIG. 200.—Branchial arterial system of _Neoceratodus_. Lateral view. The conus arteriosus and the afferent branchial vessels are represented in solid black, the efferent vessels and their derivatives with double contours. _a_, Auricle; _a.c.a_, anterior carotid; _a.cb.a_, anterior cerebral artery; _af.b.a′_, first afferent branchial artery; _br.a_, brachial artery; _c.a_, coronary artery; _c.ar_, conus arteriosus; _c.m.a_, coeliaco-mesenteric; _ep.a_, epibranchial artery; _hb.a_, hypobranchial artery; _hy.a_, hyoid artery; _hy.ar_, hyoidean arch; _l.a_, lingual; _l.d.a_, _r.d.a_, left and right dorsal aortae; _oc.a_, occipital artery; _oes.a_, oesophageal artery; _p_, pericardium; _p.a_, pulmonary artery; _p.c.a_, posterior carotid; _p.cb.a_, posterior cerebral artery; _s.v_, sinus venosus; _v_, ventricle; 1, hyobranchial cleft; 2-5, branchial clefts. (After Baldwin Spencer, diagrammatic.)] In _Neoceratodus_ (Fig. 200),[389] 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 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 backwards, 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 hyoidean pseudobranch. The efferent vessel of the pseudobranch (_a.c.a_) or anterior {339}carotid artery, eventually enters the cranial cavity and subdivides into anterior and posterior cerebral arteries for the brain, also giving off a branch which unites with its fellow of the opposite side directly behind the infundibulum. A posterior carotid springs from the epibranchial of the first branchial arch and divides into palatine, orbital, and ocular branches; and from the ventral end of the anterior efferent vessel of the second branchial arch is derived a hypobranchial artery for the heart and pericardium. The pulmonary arteries for the lung-like air-bladder have their origin from the fourth pair of epibranchial arteries.