PISCES. 



Fig. 503. 



969 



sphenoidal and alar bones; 

 and an elevator, (Jig. 502, 

 24,) which comes from be- 

 neath the orbit, and antago- 

 nizes the preceding by dila- 

 ting the cavity in which the 

 branchiae are lodged; these 

 two are the principal muscles 

 employed in respiration. 



Muscles of the operculum. 

 The movements of the oper- 

 culum are very similar to those 

 of the palato-tympanic arch, 

 and its muscles likewise con- 

 sist simply of an elevator and 

 a depressor (Jigs. 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 (Jig. 503, 

 1,1.) 



Muscles of the branchiostegous membrane. 

 These consist of a layer of fibres (Jigs. 503, 

 504, 28) running transversely across the inner 

 surface of the branchiostegons 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 Jig. 505, 32,35, 37, &c.,butto 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 



Myology of the Perch. After Cuvier. 



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 genera there 

 are considerable differences in the arrangement 

 of the muscular system which will demand a 

 brief notice. The Raidee, 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- 



