No. 3.] MUSCLES AND NERVES IN AMIA CALVA. 699 
closely and more tightly gathered in than the ventral ones, 
these latter being thus left to project loop-like beyond the neck. 
The anterior, ventral portion of the muscle lies nearly hori- 
zontal, running forward from the neck of the muscle, immediately 
dorsal to those portions of the geniohyoidei that have their in- 
sertion in median aponeurosis of that muscle, and immediately 
dorsal to the intermandibularis, but ventral to those portions of 
the superior geniohyoidei that have their insertions as a tendin- 
ous sheet on the inner surface of the mandible. It is double 
throughout the greater part of its length, the two parts lying 
close together at the middle line of the head, except near their 
front ends, where they diverge slightly, and are inserted, in 
part, on the dorsal surface of the hind margin of the interman- 
dibularis, and in part beyond that margin, on the inner surface 
of the mandible, near the symphysis. That portion of the 
muscle that has its insertion on the mandible is mainly or 
entirely tendinous, and forms a thin, tendinous sheet, which, 
in the adult, is closely applied to, and not easily separated from, 
the ventral surface of the anterior, tendinous ends of the genio- 
hyoidei. 
The posterior portion of the muscle runs upward and back- 
ward from the neck of the muscle, in front of the anterior 
tendinous margins of the hyohyoidei, and between the two 
tendons of the sternohoideus, being compressed somewhat by 
these latter tendons as it passes between them. It then sepa- 
rates at once into two portions, which diverge to the right and 
left, and are inserted on either side to the arms of a Y-shaped 
tendon (Caa4, Figs. 46 and 47, Pls. XX XII and XXXIII), which 
arises, by its median portion, from the symphysis of the clavicles, 
or from the median aponeurosis of the sternhyoideus, and is 
inserted, by its two arms, to the second and third hypobran- 
chials on each side of the head. This ligament, therefore, corre- 
sponds to one or both of those portions of the coraco-arcuales 
anteriores of Acipenser (No. 125, p. 480) that have their in- 
sertions on the second and third arches. As the insertion on 
the third arch, in Amia, is apparently the most important, and 
as the branchiomandibularis, in Acipenser, is in intimate relation 
with the tendon to the third arch, I have called the tendon or 
