320 FISHES. 



the first of the great pieces of whicli it is inserted Very frequently 

 tranverse fibres unite the tAvo genio-hyoideans into a single mass, at 

 least in their middle part,as is exemplified in the perch. A trans- 

 verse muscular band often unites one branch of the hyoid with the 

 other, but the perch has nothing like this. As for the remainder, the 

 muscles between the rays of the branchiostegal membrane act also 

 as a direct agent in bringing together the branches of the hyoid ; nor 

 ought we lose sight of that portion of the great lateral muscle of the 

 body, (No. 1), which is directed to the body of the hyoid, and per- 

 forms the function to it of a sterno-hyoidean. 



Muscles of the Branchiostegal Membrane. 



There is generally a layer of fibres (Nos. 28, 28) placed transver- 

 sely on the interna] surface of the branchiostegal rays, occupying 

 more or less space, according to the species. 



A part of these fibres arises from the internal surface of the opercu- 

 lum, towards its base ; bvit some of them also arise from the suboper- 

 culuin: they pass over the rays, adhering to them only by cellular 

 tissue. They thus form a sort of purse round each of the branchial 

 cavities, which is complete in proportion to the smallness of the 

 branchial opening, sometimes those of one side unite with those of 

 the other, under the isthmus, wholly as in eels, or in part, as in the 

 cyclopterus, or lophius : sometimes even as in eels, they are joined by 

 a raphe to the body of the os hyoides, and in general to the inferior 

 anterior part of the trunk ; but Avhen the gills are well split, these 

 communications from one side to the other do not exist. However, 

 there is often a pair of very remarkable muscles which, crossing each 

 other, pass from the inferior ray of one of the membranes to the 

 anterior extremity of the opposite branch of the hyoides (Nos. 29,29); 

 they stretch the membrane, and draw it towards that of the other 

 side. As to the fibrous layer which is placed over the rays, its 

 general effect is to bring them nearer to each other, and to contract 

 the branchiostegal membrane. 



There are also small peculiar muscles to each branchiostegal ray, 

 which have their other attachment to the neighbouring part of the 

 branch of the os hyoides, and which, according to the species and the 

 direction, contribute to dilate or contract the membrane ; but their 

 existence is not constant. They are not found in the perch ; but 

 they are easily observed in the lophius and cyclopterus. 



Muscles of the Branchial aud Pharyngeal Apparatus. 



These muscles may be divided into several groups, some suspend- 

 ing this apparatus to the cranium, some to the spine, some are attached 

 to the humeral bone, and others to tlie body of the hyoid ; finally 

 some of them are proper to the apparatus, and unite its parts with 

 each other. 



A fii'st fasciculus is attached to the cranium, between the depressor 

 muscle of the palatine arcade, and that of the opercvdum, to the part 

 of the great wing, and of the petrous bone, which lies under the 



