BLOOD-VESSELS OF MUSTELUS ANTAROTICUS. 
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girdle in front to the pubis behind. It is situated mesiad of the skin, i.e., 
between it and the abdominal muscles. It receives numerous tributaries which 
form a very beautiful plexus on the abdominal wall immediately beneath the 
skin. Anteriorly the vein trifurcates, the three branches uniting again in the 
form of a rhomboid, the lateral angles of which are connected with the lateral 
veins (fig. 14) close to the entrance of the brachial veins. Posteriorly the anterior 
ventral cutaneous vein sends off two branches, a right and a left, almost at right 
angles; these pass along the ventral aspect of the pubic cartilage, turn round 
the outer border of the latter, and then, passing inwards parallel to and dorsad 
of their former course, anastomose with the iliac veins (figs. 3 and 14). 
10. The Posterior Ventral Cutaneous Vein 
(Plate 34, fig. 3 ; Plate 36, fig. 14, Post. vent. cut. F.) lies in the middle ventral line of 
the caudal region. Passing forwards from the tail it forms a loop round the base of 
the ventral (so-called anal) fin (fig. 14, V. f.) like those formed round the dorsal fins 
by the dorsal cutaneous vein. Arriving at the hinder wall of the cloaca it bifurcates, 
the two branches anastomosing each with the corresponding cloacal vein. 
There is thus direct communication, through the cloacal and iliac veins, between the 
anterior and posterior ventral cutaneous veins ; indeed, they might almost be described 
as a single vessel forming loops round the anal fin and the cloaca. It will be noticed 
that there is a curious parallelism between these vessels and the sub-intestinal vein, 
which, in its early state of entirety, forms a loop round the cloaca. 
11. The Lateral Cutaneous Vein. 
Tronc lymphatique lateral sous-cutane, Pobin, cpioted by Milne Edwards 
(15). 
The lateral cutaneous veins (Plate 36, figs. 14 and 16 ; Plate 37, figs. 22 and 24, 
Lat. cut. V.) are paired longitudinal vessels, extending along the side of the trunk and 
tail at the junction of the dorsal and ventral muscles. Like the ventral cutaneous 
veins, they lie immediately beneath the skin. They anastomose posteriorly both with 
the caudal and with the dorsal cutaneous vein (fig. 14) ; anteriorly each discharges into 
the corresponding subscapular sinus (figs. 14 and 16). 
General Considerations. 
One of the most striking features of the blood-vessels of Selachians, as represented 
by Mustelus antarcticus, is the number of large anastomotic trunks between important 
arteries and veins. In the arteries there are commissures uniting the anterior and 
posterior carotids (Plate 35, fig. 6, iv), others placing the efferent arteries of each 
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MDCCCLXXXVI. 
