350 FISHKS. 



There are some very thick, of quite a stony nature, which are but 

 sh'ghtly imbricated, but very compact, and form for the fish a true 

 cuirass, such are those of the Icpisosteus, the birchir, &c. 



In certain fishes, as the eel, the scales are not at all imbricated, and 

 have all their parts equally incrusted under an epidermis rather thick; 

 nevertheless they are sufficiently approximated. 



In others, such as the turbot, and cyclopterus, there are scales simi- 

 lar to cones or tubercles more or less bristly, which adhere to the 

 skin by tlieir large base, and between which are naked intervals. 



Similar scales, but reduced to very small points, cover the bodies of 

 the greater part of the teti'odons. In the diodons these points become 

 long thorns, whose base widens to support them as tripods. 



The grains which make the skin of the scyllyum and the majority of 

 chondropterygians very rough, are also species of scales, and when 

 they take the form of soft tubercles, which touch each other and which 

 may be polished, they give it what is called the galuchat, an armour 

 which belongs to the sjiecies of stingrays. There are some whose form 

 and size make a complete buckler, such as are those of the sturgeon. 

 Tliose scales which are mostly developed, and which best shew their 

 analogous nature to that of teeth, are those to which the name ray 

 buckles has been given. Their base, which is oval and puffed, is 

 hollow in the interior, and in them it penetrates the vessels which 

 nourish a pulpy nucleus very similar to that of a tooth. 



The cuirass of the ostracions is only formed of a collection of large 

 scales or plates, whose edges are in contact, and thus become neces 

 sarily angular. 



It is the dermis which secretes beneath the scales the matter of a 

 metallic silvery colovir, which causes the brilliancy in fishes; it is 

 composed of small polished lamina, like burnished silver, which are 

 removed by washing cither from the skin or from the scales, the under 

 surface of which they varnish. It is well known that it is this 

 matter with which false pearls are coloured. It is also secreted, in 

 many fishes, in the thickness of the peritonoeum and the coats, fur- 

 nished to certain viscera, particularly to the natatory bl dder*. 



The scales are not equally spread, neither are they of similar form 

 or consistence over the whole body. Frequently the head is deprived 

 of them, and is only defended by the wrinkles and roughnesses of its 

 bones, covered with a skin very thin and very closely adherent ; but 

 it also happens that they may have, according to their genera, scales 

 upon the cheek, on the opercular pieces on the cranium, and even on 

 the snout and jaws, and, lastly, on the branchiostegal membrane 

 itself. The scales extend also m.ore or less, on the fins, and even in 

 the squammipennes. The dorsal and anal fins are covered in almost 

 the same manner as tlie rest of the body. 



The scales of the lateral line are distinguished from others by one 

 or more small tubes with which they are bored, and frequently by 

 other peculiarities. In the caranx, for example, they rise in ridges 

 on both sides of the tail. 



* See a Memoire of M. E^aumur upon this silvery matter, amongst the me- 

 moirs of the Academic des Sciences for 1 816, p. 229. 



