50 ALLEN 
cavity a little to the right of the median line, the ventral artery 
gives off numerous branches to the sternohyoideus muscle. In 
the specimen from which fig. 12 was drawn, a vessel was 
noticed branching off to the left, passing horizontally under 
the ventricle, and terminating on the left precaval vein in the 
neighborhood of the left subclavian sinus. Directly caudad of 
this vessel and a little cephalad to the crossing of the sinus 
venosus, the ventral artery sends off a pair of vessels to the 
ventral muscles of the pectoral fin. Each of these hypobranch- 
tal arterzes (Pl. Il, figs. 12 and 14; Hypobr.A.) runs a short 
distance caudad between the sternohyoideus and the pectoral 
profundus adductor muscle, and then curves slightly dorsad, 
passing between the inner surface of the coracoid and the pec- 
toral profundus adductor muscle, giving off at least two branches 
to the inner surface of the muscle; then curving slightly ven- 
trad, penetrates the basal canal of the pectoral rays,’ and 
anastomoses in this canal with the zzternal subclavian artery 
(2) (Pl. Il, fig. 14; I. Sub.A..,,), but before entering this canal 
the hypobranchial gives off a dorsal branch which passes be- 
tween the pectoral profundus muscle and the brachial ossicles, 
supplying the inner surface of the muscle. Continuing caudad, 
the ventral artery passes under the sinus venosus between the 
pelvic bones, giving off arteries to the body wall, the ventral 
or pelvic fin muscles, and the ventral rays. The first con- 
stant artery of any size to be given off from the ventral artery 
after it reaches the ventral fin musculature is one which comes 
out ventrad in a median line to the outer surface of the pro- 
tractor muscle of the pelvic arch, where it divides at nearly 
right angles, one branch supplying the left, the other the right 
protractor muscle of the pelvic fins and the very large abductor 
muscle of the ventral spine (fig. 12; Ab.V.S.). At various 
intervals, usually alternating with the veins, the ventral cnter- 
costal arterves (Pl. Il, fig. 12; V.Intc.A.) are given off between 
every alternate pair of myotomes, and they anastomose with the 
corresponding dorsal intercostal arteries. The ventral artery 
‘Each pectoral fin ray consists of 2 separate halves, which are concave inside 
and convex outside, and where their bases overlap the brachial ossicles in their 
attachment to the shoulder-girdle, there is formed a rather large canal at the 
base of the pectoral fin. 
