Paired Arteries. (Fig. 2.)

In Typhlonarke the subclavian arteries arise symmetrically posterior to the fourth epibranchial arteries. An ovarian branch (ov.) is given off, running posteriorly, parallel to the dorsal aorta, then another branch runs to the dorsal musculature (d.m.). The coracoid artery (cor.) joins the subclavian artery after passing dorsal to the coracoid cartilage and arising from the hypobranehial system as described above. In Typhionarke the coracoid artery is very fine in comparison with the wide vessel in R. nasuta. In R. nasuta the subelavian artery receives the coracoid artery at a point just median and ventral to the division into the propterygial and metapterygial arteries. From the propterygial artery about two centimeters from where the subclavian divides, a branch passes round dorsally to the anterior side of the propterygial cartilage. A ventral abdominal branch (Fig. 2, B, v.a.a.) from the metapterygial artery runs medioposteriorly on the dorsal side of the metapterygial cartilage along the ventral body wall to join the iliac artery. From the subclavian there arises the lateral abdominal artery (l.a.a.), which passes along the side of the body cavity and joins the femoral artery lateral to the ventral abdominal artery.

In Typhlonarke the iliac arteries have cloacal arteries arising from them, of which the right one is the larger. A dorsal artery (d.m.) supplies the dorsal muscles, and the iliac artery then supplies the fin. A branch of fair size is given to the anterior basal cartilage and also supplies the first few radials. The remainder of the radials are supplied by an artery which proceeds backwards, dorsal to the radials and lateral to the basipterygium.

In R. nasuta (Fig. 2, B) two spermatic arteries arise median to the cloacal arteries and pass anteriorly. After receiving the ventral abdominal and then the lateral abdominal arteries, the iliac artery divides in the fin. In R. montagui a branch from near the base of