338 FISHES CHAP. 
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 Neoceratodus (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 
LB f ! 
ea Gis 
Fie. 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 ; ¢.a7, conus arteriosus ; ¢c.m.a, coeliaco- 
mesenteric ; ep.a, epibranchial artery ; hb.a, hypobranchial artery; hy.a, hyoid 
artery ; hy.ar, hyoidean arch ; /.a, lingual ; U.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.cbh.a, posterior cerebral artery ; s.v, sinus 
venosus ; ¥, 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 hyoidean pseudobranch. 
The efferent vessel of the pseudobranch (a.c.a) or anterior 
1 Baldwin Spencer, Macleay Memorial Volume, 1892, p. 1. 
