140 Cc. H. DANFORTH 
Muscles of the anal fin 
The muscles of the anal fin correspond exactly with those of 
the dorsal fin except in number. Here there are only eighteen 
radialia and the pairs of muscles on each side are correspondingly 
reduced. 
Innervation. The innervation corresponds with that of the 
dorsal fin except that the branches are here derived from the 
ventral rather than from the dorsal divisions of the nerves in- 
volved. The most anterior nerve to the anal fin is number 
thirty-four. 
Action. The action of these muscles is also comparable to that 
of the dorsal fin. 
Muscles of the caudal fin 
As already stated, the lateral muscle of the body is the main 
muscle of the tail, and in its action it corresponds more nearly 
with that of the muscles of the fins already described. There 
is, however, in the caudal fin, an incomplete double set of oblique 
muscles extending between the cartilaginous rays. The super- 
ficial muscles run backward and toward the mid-horizontal plane, 
the deep muscles cross these obliquely. In the upper part of 
the dorsal lobe of the tail, which is encased in a bony covering, 
these muscles are nearly or quite lacking. 
Innervation. The nerve supply is from two longitudinal trunks 
that result from the union of branches of a number of the most 
posterior spinal nerves. 
Action. These little muscles seem to be divaricators of the 
rays. 
VIII. MUSCLES OF THE PECTORAL ARCH 
The muscles of the pectoral arch are described as abductors 
adductors and trapezius. <A few fibers of the great ventral mus- 
cle are also attached to the arch but they are not sufficiently 
differentiated to warrant a separate description. In keeping with 
the simple condition which obtains in this fish, deep and super- 
ficial abductors and adductors are not separated from each 
other. ‘These deep and superficial muscles, in forms where they 
