PISCES. 
Fig. 503. 
969 
Myology of the Perch. After Cuvier. 
sphenoidal and alar bones; 
and an elevator, (fig. 502, 
24,) which comes from be- 
neath the orbit, and antago- 
nizes the preceding by dila- 
ting the cavity in which the 
branchie are lodged; these 
two are the principal muscles 
employed in respiration. 
uscles of the operculum. 
—The movements of the oper- 
culumare very similar to those 
of the palato-tympanic arch, 
and its muscles likewise con- 
sist simply of an elevator and 
a depressor (figs. 504 & 505, 
25, 26.) 
Muscles of the os hyoides. 
—The principal of these 
(figs. 503 & 505, 27) seems 
to correspond to the genio-hy- 
oideus, and has a similar of- 
fice ; its antagonist is a pro- 
longation of the great lateral 
muscle of the body (fig. 503, 
1, 1.) 
Muscles of the branchiostegous membrane.— 
These consist of a layer of fibres (figs. 503, 
504, 28) running transversely across the inner 
surface of the branchiostegous rays; this is 
in some Fishes assisted by accessory muscular 
_fibres derived from the os hyoides. 
Muscles of the branchial and pharyngeal 
apparatus.—These must be divided into several 
groups, some of which connect this apparatus 
with the skull, others to the spine, others to the 
humeral bone, and others to the os hyoides ; 
while some connect one part of the apparatus 
to another. Their general distribution is shewn 
in fig. 505, 32,35, 37, &c., but to describe them 
more minutely would carry us beyond our 
limits. 
In the Ostracions, or box-fishes, which have 
their entire body, with the exception of their 
jaws and fins, enclosed in a dense case of ar- 
mour, the arrangement of the lateral muscles of 
the trunk is considerably modified; they oc- 
cupy, indeed, the same situation, but are only 
attached at the head and tail. In this case 
Fig. 504. 
Myology of the Perch. After Cuvier, 
insertions into the vertebral column would have 
been useless, seeing that the tail is the only 
moveable part. The texture of these lateral 
muscles is also much simpler, their fibres 
being almost all longitudinal. The ribs are 
entirely wanting, these parts being replaced by 
a silvery aponeurosis, which forms the walls of 
, the abdomen and lines the interior of the shell. 
In the Plagiostome cartilaginous generathere 
are considerable differences in the arrangement 
of the muscular system which will demand a 
brief notice. The Raide, or Skates, for exam- 
ple, so remarkable for the construction of their 
skeleton, are not less so in respect to the dispo- 
sition of the muscles that move its different 
parts. In these fishes the muscles of the trunk 
resemble very strikingly those which are met 
with in the tails of quadrupeds. They are four 
in number, arranged upon two planes, so that 
there are two superior lateral and two inferior 
lateral muscles. 
The superior laterals arise from the middle 
portion of the vertebral column above the abdo- 
