In _Neoceratodus_[366] (Fig. 191) the renal portal system is unusually complex, the veins distributing venous blood to the kidneys being derived from several sources, as follows: (1) from each of the two branches into which the caudal vein divides on its exit from the haemal canal (_af.r.v_); (2) from a common trunk (_pt.v_) which, on each side, is formed by the union of segmental veins from certain of the post-cloacal myotomes and is united with its fellow by a transverse anastomosis; (3) from more anteriorly situated intercostal or segmental veins (_i.c.v_) which enter each kidney directly; and (4) from a vein on each side corresponding to the renal portal vein of Amphibia. The latter vein (_rp.v_) is formed by one of the two branches of the iliac or femoral vein, and joins {324}the corresponding vein from the caudal myotomes; from the common trunk numerous branches enter the kidney. [Illustration: FIG. 191.—Venous system of _Neoceratodus_. _a.ab_, Anterior abdominal; _af.r.v_, afferent renal veins; _b.v_, brachial; _c.d_, Cuvierian duct; _c.v_, caudal; _h.p.v_, hepatic portal; _h.v_, hepatic; _i.c.v_, intercostal veins; _i.j_, inferior jugular; _il.v_, iliac; _i.v.c_, inferior vena cava or postcaval; _k_, kidney; _l_, liver; _l.a_, left auricle; _l.p.c_, left posterior cardinal; _l.v_, lateral cutaneous vein; _pt.v_, vein from postcloacal myotomes; _p.v_, pulmonary vein; _pv.v_, pelvic; _r.a_, right auricle; _rp.v_, renal portal; _s.c.v_, subscapular; _s.j_, superior jugular or anterior cardinal; _t_, testis; _v_, ventricle; _v.v_, right vertebral vein. (After Baldwin Spencer.)] In the derivation of renal portal veins from each of the two veins into which the caudal vein divides, _Neoceratodus_ approaches the Elasmobranchs. On the other hand, the utilisation of ordinary segmental veins from the caudal and pre-caudal myotomes, some of which directly enter the kidney, is a feature which has already been remarked in some Teleosts; while the formation of a renal portal affluent by a branch of the femoral vein is an even more striking Amphibian characteristic. The efferent renal veins[367] join the root of the left posterior cardinal and the adjacent portion of the caudal vein.