PECTORAL SKELETON OF TELEOSTEANS. 375 
in the muscle canal (m. c.), sending one branch (n. 1—3d) to 
the dorsal muscles, and the other (n. 1—3v) through the 
scapular foramen to the ventral muscles. 
The fourth nerve (n. 4) likewise bifurcates, sending one 
branch to a plexus which supplies the dorsal muscles, and 
the other through a passage (fn. 4) to the ventral muscles. 
The entrance to this passage was seen by Parker and called 
the “coracoid foramen,” but was overlooked by Gegenbaur. 
It evidently corresponds to the postcoracoid foramen. The 
fifth spinal nerve (7. 5) repeats the conditions of the fourth 
with this difference, that its ventral branch has no foramen, 
but passes to the ventral fin muscles by way of the inner 
side of the metapterygium. ‘Thus the anterior part of the 
“primares basale” is represented by that portion of the 
girdle which lies between the glenoid facettes and the 
scapular and postcoracoid foramina, whilst the posterior part 
becomes the metapterygium. ‘This is proved to be the case 
by Mollier’s figures. 
Whilst the metapterygium has retained the primitive 
position parallel to the axis of the body, the girdle has 
rotated so that the glenoid border, whilst still horizontal, is 
nearly at right angles to this axis. The radial elements upon 
it no longer project at right angles, as they must have done 
in early fishes, but are almost parallel to the metapterygium. 
Herein, then, lies a cause for the reduction in number and 
importance of the radials borne by the metapterygium. 
Thus the latter, instead of rotating out to become the main 
bearer of the fin skeleton, as in other fishes than the 
Teleostomes, remains in the body-wall, and becomes a minor 
factor. 
All these changes are probably associated with the in- 
creasing importance of the dermal fin rays, and with the 
acquirement of the power to lay that portion of the fin 
flat against the side of the body, or to extend it so that it 
may act as a brake instead of a keel.! 
1 Thope to publish soon an account of some experiments which illustrate 
this point more fully. 
vou. 49, PART 2,—NEW SERIES, 26 
