PECTORAL. SKELETON OF TELEOSTEANS. 365 
at a later stage, though there is no sign of its formation at 
present. At this early stage the glenoid line is practically 
parallel to the long axis of the animal’s body. 
The girdle is triradiate with a large fenestra (fn. 4) at the 
junction of the radii. Through this there passes a branch of 
the fourth spinal nerve to supply the ventral muscles of the 
fin, and also a small artery and vein. 
The dorsal radius is the scapulo-coracoid region (sc.co.). It 
is continuous with the fin-plate along its upper, and is folded 
inwards on its lower, border (fig. 2). The inner edge of the 
fold bears a slight outgrowth—a kind of scapular process (sc.) 
near its anterior end. Posteriorly it is much thickened, and 
bears a much stronger outgrowth (m.), which is the first trace 
of the mesocoracoid bar. Ata point (jf. 1—3) lying a short 
distance internal to this folded edge, and between the two 
outgrowths, a stout nerve forks, sending one branch to the 
true dorsal, and the other to the ventral, surfaces of the fins. 
This nerve is formed by the union of the first three spinal 
nerves. , ne 
The anterior radius (pr. p.) is long and rod-like, and looks 
almost like an antero-ventral continuation of the mesocoracoid 
thickening. Ata later stage it trends medianly and meets its 
fellow of the opposite side in the middle line. At this stage, 
however, owing to the size of the yolk-sac, it bends somewhat 
laterally. Gegenbaur, and Swirski following him, calls this 
the procoracoid. ‘I'he latter describes it as arising independ- 
ently from the rest of the pectoral skeleton in the pike. But 
though Wiedersheim has investigated the same fish he finds 
no evidence for this independence. Neither from Ducret’s 
observations nor my own on the salmon is there anything in 
support of this. It will be sufficient, therefore, to regard it 
as a process of the coracoid, and to call it the preecoracoid 
process. 
‘The posterior radius (po. p.) stands nearly at right angles 
to the general plane of the girdle and the fin-plate. It runs 
for a short distance from the post-axial border of the latter 
into the body wall. It corresponds to the “ coracoid” of 
