THE MYOLOGY OF POLYODON 135 
From the base of this half cone, which opens caudally, there are 
two wings, one extending ventrally the other dorsally. They 
separate from each other at the level of the lateral line. The 
ventral wing runs obliquely backward and downward to meet 
the ventral musculature. The lateral margin, being more pos- 
terior than the medial, is overlapped by the preceding, and itself 
overlaps the following segment. The dorsal wing of the myomere 
at first runs diagonally back and up and then folds on itself so 
as to run forward and up, terminating as far anterior as the 
point from which it originated. Where this wing of the myo- 
mere bends forward a pocket is produced with its opening directed 
forward. This results in the formation of a true cone, the apex 
of which reaches further caudad than any other part of the 
myomere. It fits into the posterior cones and is filled by those 
in front of it like a nest of beakers. Above the lateral line all 
the myomeres are essentially similar, but below, their form 
changes somewhat both anteriorly and posteriorly. In front, 
from the fifth myomere on, the ventral wing bends forward below, 
and its margin is also rolled outward somewhat, thus producing 
a kind of incomplete cone-like formation. Behind the ventral 
fins the succeeding myomeres end relatively further and further 
forward and this consequently results in the formation of caudally 
pointed cones and a duplication of the upper half of the muscula- 
ture so that the epaxial and hypaxial portions come to be similar 
to each other. ; 
Innervation. The postvagal nerve root joins the first spinal 
nerve at some distance from its point of emergence from the 
skull, and lower than the level at which the branches to the 
lateral muscle are usually given off. Nevertheless it is possible 
that a few of its fibers do reach the first segment, although it 
is much more probable that they are all destined to the hypo- 
glossal musculature. The fifty-eight spinal nerves each give rise 
‘to dorsal, lateral, and ventral branches. The large lateral branch 
is very short and enters the corresponding myomere directly. A 
small dorsal branch follows the edge of the myomere upward 
and the main ventral branch follows the lower wing of the myo- 
mere downward. 
