38 Natural History and Anatomical Description 



The posterior extremity is far from presenting so many 

 points of resemblance with that of the mammaUa. The 

 limb (4 lines) is exceedingly short in regard to the fin 

 (l inch 5 lines) ; besides, it is composed of only five bones. 

 The first, which, with its fellow, performs the office of a 

 pelvis, is long and flat, and terminates in a broad base, at 

 the extremity of which are articulated four small elongated 

 and parallel tones. The protecting apophyses of the radii, 

 though extremely short, envelop, however, on each side, 

 the extremity of these small bones ; which is possible, be- 

 cause each radius composed of two lamina is terminated by 

 a double apophysis. 



This organization i* seen on a more extensive scale and 

 more distmctly in the anal fin ; where each radius, com- 

 posed of two triangular laminae, united only by their ante- 

 rior edge, is disposed in such a manner that the first radius 

 receives the second, the second the third, the third the fourth, 

 and so on. 



The dorsal exhibits a fact of organization no less curious 

 than what has been described. It is composed of sixteen, 

 seventeen, or eighteen osseous radii, eleven hues in length, 

 separated from each other, compressed transversely, of 

 equal breadth, that is to say three lines, and terminating 

 in two sharp points. These osseous laminae, by rising up 

 alonii; the \\ hole back, present in case of need a formidable 

 armour. That these laminae, however, may have a base 

 proportional to their solidity, they are articulated directly 

 with the upright apophyses of the vertebrae, and not, as in 

 the other fishes, with the protecting apophyses of the radii :, 

 for this purpose the upright apophyses of the vertebras are 

 stronger, and terminated by a head destined for the articu- 

 lations of the radii. The protecting apophyses, by this 

 sin""ular arrangement, become useless ; they however exist, 

 but arc smaller, and inserted under the skin in the' cellular 

 tissue : they are merely the rudimenbs having a little more 

 development. 



The dorsal radii are not only transformed into a double- 

 pniiited dart; but each of them also is a parlicnlar fin ; for 

 there arises from the posterior surface of the laminae a trans- 

 parent membrane, which far exceeds the radius itself (or 

 1 inch 6 lines), v.hich is supported towards the upper part 

 by four small round cartilaginous radii, having each a 

 particular origin. Thi» series of small fins is prolonged 

 without interrujjtion as far as the caudal fin, so that they 

 are distinguished only by llic difllrence of their radii. 



The tail is very short, eumpressed on the sides, and ter- 

 minates 



