FISHES. 303 



articulations, most frequently ramified into a certain number of 

 branches, which are again subdivided into other branches; they are 

 called articulate rays, soft, or branched rays. 



Very frequently, and perhaps always, these rays, even those we 

 have just called simple, are divided longitudinally by a suture, into 

 two halves, one on the right, the other on the left. 



The rays of the caudal fin (No. 71) are always soft and articulated, 

 but at its root above and below, it has small ones (Nos. 78, 78) 

 which diminish insensibly in front, where the solid part of the base 

 alone remains. 



We may here observe, that the caudal fin has almost always, a ray less 

 in its lower half than in the upper ; but to this rule however, there are 

 exceptions. 



In a great number of fishes, the vertebrae at which the abdomen 

 terminates, and the tail commences, and even the vertebrae following 

 it, (Nos. 83, 83) have large inferior spinous apophyses, to which is 

 joined a bone of more or less bulk. (No. 79)> which descends to the 

 back of the anus, thus limiting behind the cavity of the abdomen. 



In the perch this is still a simple inter spinal, as our figures shew, 

 (No. 79 ; but in other species it appears to result from a very large 

 development of the first interspinal of the anal fin, or of the soldering 

 together of some of the first of these bones : it is nevertheless a fact, 

 that it fulfils a part of the functions of the pelvis. 



The first interspinals, both inferior and superior, are in certain chce- 

 todons, swelled into thick knobs. 



It is not necessary to enumerate in this place, the varieties in num- 

 ber, position, size, and length, of which the rays are susceptible. 

 These circumstances may be observed externally, and serve even to 

 give the character of species. We shall take notice of certain rays, 

 which extend even on the head, by means of an inter-spinal, which 

 lies fiat on the cranium, and which in this position represent so many 

 sorts of panache; these are seen in the lophius, in certain blennies, &c. 

 We shall also remark that in some genera, principally of the family of 

 the scombres, the spinous rays of the anterior part of the dorsal, and 

 more frequently still a part of the soft rays of the dorsal and the anal, 

 are not joined to the others by complete membranes, and they form 

 what is called for the first, the free spines, and for the others, false 

 fins. The sternum is deficient in very nearly the whole of the fishes ; 

 when it does exist, it forms a series of azygos bones, varying in their 

 shapes according to the genera to which the ribs are attached . It is 

 seen chiefly in the herrings and the vomers. 



Of the Shoulder and Arm* 



In the osseous fishes immediately behind the aperture of the gills, a 

 series of bones is observed on either side, which circumscribes this 

 aperture at the back part, forming a sort of jamb, on which the oper- 

 culum falls when it closes. 



These two series are most generally attached to the upper part of 



* Independently of what is stated in general works, a special memoir on the 

 shoulder of fishes by M. Geoffroy St. Hilaire, in the ix vol. of the Annales du 

 Museum, p. 3, 5, 7, which is the origin of the researches of this learned naturalist 



