64 ALLEN 
spine; and in the specimen from which fig. 16 was drawn, the 
levator muscle of the second dorsal spine, as well as sending up 
a branch behind the first dorsal spine. 
After giving off the first neural artery the subclavian might 
be designated as the brachial artery as in mammals, but it 
seems hardly advisable to press such homologies. Emerging 
from the head kidney the subclavian passes ventrad along the 
inner anterior surface of the pectoral superficial adductor mus- 
cle; and when the pectoral profundus adductor muscle is 
reached, a branch is given off to the superficial muscle; then 
bifurcating, forms what I have designated as the external and 
internal subclavians.' The zxternal subclavian artery (P|. Il, 
fig. 14; I.Sub.A.) for a short distance continues along the 
inner cephalic edge of the superficial adductor muscle; then 
divides into a superjfictal internal subclavian artery (P1. Il, fig. 
14; I.Sub.A.,,), which after giving off a few branches to the 
superficial adductor muscle continues obliquely ventrad along 
the inner surface of the profundus adductor muscle; and a pro- 
Jundus internal subclavian artery (Pl. Il, fig. 14; I.Sub.A..,), 
which immediately penetrates both superficial and profundus 
adductor muscles and runs obliquely ventrad between the pro- 
fundus muscle and the scapula, giving off several branches to 
the former. In the neighborhood of the most dorsal pectoral 
ray this vessel divides into a brachial ossicle artery and a pec- 
toral fin artery. The brachial ossicle artery crosses these bones 
in its ventral course just back of the pectoral rays, and ex- 
hausts itself by giving off vessels to the distal part of the pro- 
fundus muscle and by sending off branches between the ossi- 
cles to the profundus muscle on the outside of the shoulder- 
girdle. While the pectoral fin artery penetrates the basal canal 
(see note, page 50) between the first, or most dorsal, and the 
second rays, and continuing ventrad in this canal anastomoses 
with the hypobranchial artery. Throughout its entire course 
it gives off a branch to the central canal of each ray, which 
soon divides, one branch continuing along the dorsal side of the 
cavity and the other along the ventral side. The external sub- 
clavian artery (Pl. Il, fig. 14; E.Sub.A.) immediately passes 
'Perhaps external and internal pectoral arteries would be better names. 
