732 ALES: [VoL. XII. 
The course of the outer edge of the first intermuscular 
septum has been given. The second runs from the mid-dorsal 
line, outward and backward, approximately along the posterior 
edge of the extrascapular. It then turns abruptly downward 
and forward, and runs between the posterior end of the supra- 
scapular and the anterior and upper end of the supraclavicular. 
The third septum reaches the under surface of the supracla- 
vicular near its upper end. It then turns downward and back- 
ward, and is attached to the corium, approximately opposite 
the anterior end of the first scale of the lateral line. The 
same part of the fourth septum corresponds, approximately, to 
the anterior end of the second scale of the lateral line, etc. 
The seventh septum lies close against the inner, posterior sur- 
face of the muscles of the pectoral fin, and is the first septum 
that extends unbroken from the mid-dorsal to the mid-ventral 
line. Between the ventral end of this septum and the ventral 
end of the clavicle, below the fin, there were, in the several 
specimens dissected, but one muscle segment and no muscle 
septum. The sixth septum always ended as a ligament attached 
to the clavicle at the lower edge of the fin, and the fifth as a 
similar ligament attached to its upper edge. The fin always 
lies in a deep impression in the trunk muscles, the muscle mass 
being pushed inward so that its anterior edge, at this place, lies 
internal to the inner edge of the clavicle. By this arrange- 
ment the sixth segment is apparently cut off. As there are, 
however, muscle fibres between the sixth septum and the clavi- 
cle, above the fin, the clavicle, at its ventral end, probably corre- 
sponds to the fifth intermuscular septum, that is, to the septum 
that has its attachment to the second occipital arch. The 
sternohyoideus, which lies in front of the clavicle, thus belongs, 
in its relation to the muscle segments, as it will be shown that 
it does in its innervation, entirely to the region of the head, 
and not in part to the trunk. 
In one specimen shown in Fig. 34, Pl. XXVIII, the septa 
were still further complicated, for the seventh septum had been 
pushed back by the fin against the eighth septum, and was 
found partly fused with that septum. The eighth septum had 
a surface septal connection with the ninth septum. In front 

