338 
EDWARD PHELPS ALLIS. 
of each arch unite ventrallv to form a small bundle. This 
bundle contracts to a small and pointed head, which, passing 
anterior (external) to the ventral extrabranchial of its arch 
and anterior to the musculus coracobranchialis of its arch, 
between that muscle and the next anterior coracobranchialis, 
is inserted on the dorsal surface of the hypobranchial muscles. 
These bundles are always referred to, in all descriptions of 
these muscles, as parts of the musculi interbranchiales, but it 
is to be noted that they are in reality the ventral ends of 
continuous dorso-ventral fibres of the constrictores, no inter- 
branchiales having been cut out of these particular fibres by 
insertions on the extrabrancliials. Convenience of descrip- 
tion, however, requires that they be considered to form 
parts of the interbranchiales. The more distal strands of 
each musculus interbranchialis extend either from the dorsal 
to the ventral extrabranchial of their arch, or from the 
related dorsal linear aponeurosis to the ventral extrabranchial, 
lying along the anterior (external) surface of the branchial 
rays of the arch, between those rays and the posterior wall 
of the next anterior gill-pouch. Certain of the branchial 
rays, in certain of the arches, have cut through the muscle 
in places, and there give insertion to the cut ends of the fibres. 
Thecoracohyoideusand coracobranchialis I are both inserted 
on the basihyal, the coracobranchiales IT, III, and IV each 
mainly on the hypobranchial of the related arch, but also 
partly, in arches II and III, on a small cartilage interpolated 
between the hypobranchial and ceratobranchial, and corre- 
sponding, in position, to the most dorsal one of the three 
cartilages marked Hbr II in Furbringer’s figures of Torpedo 
ocellata (1903, Fig. 21, PI. 17). In the fourth arch this 
independent cartilage has either fused with the ventral end of 
the ceratobranchial or has not separated from it, and the 
coracobranchialis is accordingly there partly inserted on the 
ceratobranchial. In the first branchial arch the cartilage is 
found lying between the ventral end of the ceratobranchial of 
that arch and the basihyal. The most anterior hypobranchial is 
related to the second branchial arch, as shown in FurbringePs 
