FISHES. 301 



shall then expose the singular structures of the anterior part of the 

 spine in the ophidiae,the cobites, the cyprins, the silures, the knots of 

 certain choetodons, &c. ; we shall at present confine ourselves to ob- 

 serving, that the number of the vertebrae is not always in proportion 

 to the length of the fish. 



The ribs* 



The ribs (Nos. 72, 72) have in general only one head, they adhere 

 each to a single vertebra, as in lizards, and the sternal portion is 

 wanting, if we do not regard as such, in the fishes which have a kind 

 of sternum, the scaly pieces that form it, or the aretes that join it.f 



Frequently the ribs, or several ribs, have by way of appendage, one 

 or two styles (Nos. 73, 73) adhering to some point of their length, 

 which take a direction outwards, and penetrate the flesh; some of 

 these styles, sometimes are given out from the body of the vertebrae 

 above the rib, to penetrate into the flesh; it is in this manner that the 

 crests in fishes are multiplied ; a well known example of this is found 

 in the family of herrings, whose entire flesh is traversed by crests as 

 fine as hairs. The ribs themselves vary greatly ; now slender and 

 round, but more or less robust, now compressed, or in a form of a 

 cythe, short, &c. 



In certain fishes, such as the cyprins and herrings the ribs adhere to 

 the vertebrae by means of a small intermediate bone, which is inserted 

 into a lateral cavity of the body of the vertebra, and of which it 

 forms a transverse apophysis, though capable of being detached 

 from it. 



As the ribs take no part in the respiration of fishes, their mobility 

 in general is not considerable ; there are species in which they enclose 

 the whole abdomen, fixing themselves below in such a manner as to 

 remain almost immoveable, Some fishes possess only the rudiments 

 of ribs, in others they are entirely wanting ; but the latter class is not 

 so numerous, as it has been supposed. 



Vertical Fins. 



Supported by rays, as in the four members the vertical fins, of 

 fishes can, however, only be compared, in other vertebrated animals 

 to the ridges which elevate the back of certain lizards ; still these 

 ridges are but scaly and cutaneous fringes, but the rays of the fins 

 belong in reality to the skeleton. 



Each ray is composed of an internal part called the interspinal 

 bone (Nos, 74, 7i)% which penetrates into the flesh between the great 

 lateral muscles, and serves as a sort of root,|| and of an external part 

 (Nos. 75, 75) which is the ray properly so called. 



* There is a drawing of a single rib, pi. iii. fig. 10, 72 and 73. 



•f We should recollect that M.M. Auteureith and Geoffroy professed to find the 

 sternal rib in the rays of the branchiostegal membrane, but this is a mere hypo- 

 thesis liable to dispute. 



JM. Meckel calls them accessory spinal apophyses ; these bones are represented 

 in their different aspects, with the rays they support, pi. III. fig. x. from 7-1 to 79. 



|| I know not why it has been stated that the interspinals are wanting in the 

 bichir ; like other osseous fishes, it has as many of them, as it has of rays or false fins. 



