20 Macueay Memorrat Vous. 
The renal portal system is thus of considerable extent, and the system will be 
again referred to after the remainder of the venous system has been described. 
C. Anterior abdominal system (figs. 7 and 16). 
Ceratodus possesses veins which may in all probability be rightly regarded as 
forming an anterior abdominal system comparable to that obtaining in Amphibia ; 
though, at the same time, there exist considerable differences between the two. 
Commencing now with the iliac vein, we find that, shortly after leaving the hind 
limb and after it has passed round to the inner side of the pelvic plate, it divides into 
two branches ; one of these forms the renal portal vem above described, the other 
passes forwards across the inner face of the pelvic plate and the vein thus formed on 
either side of the body gradually runs towards the mid ventral line. One comes to 
lie on each side of the anterior process of the pelvic plate and just in front of the 
termination of this (fig. 7) the two are united by a small transverse vessel and almost 
immediately join together to form a single median vessel which runs forwards in the 
mid ventral line. Each of the constituent vessels may be called a pelvic vern (fig. 7) 
and each of these receives small branches from the muscles of the ventral body wall. 
The single median vessel formed by their union at first lies considerably nearer 
to the inner than to the outer surface of the body wall; but towards the anterior end 
it gradually comes to lie nearer to the external surface though never so close to it 
as in the case of the lateral cutaneous veins. Arrived at the posterior surface of the 
pectoral girdle it turns to the right and passes dorsally through the diaphragm 
bounding the body cavity anteriorly until it passes into the pericardium and enters 
the sinus venosus immediately to the right of the entrance of the right hepatic vein 
(fig. 17). This system will also be referred to again later. 
D. Hepatic portal system (figs. 9, 11, 12, and 16). 
As in the case of the cceliaco-mesenteric artery, the ves forming this system 
have undergone considerable modification when compared with those, for example, of 
an Elasmobranch, in consequence of the relatively short alimentary tract of 
Ceratodus. Notwithstanding this they show a striking resemblance to vessels 
present in such a form as Mustelus especially in the development of an intra- 
intestinal vessel forming the vein of the spiral fold which is further to be regarded 
as a persistent relic of the primitive subintestinal trunk. 
