THE P LEG TOG HA Till. 
287 
head and body being grayish-green glossed with bine, the abdomen silvery- white, and the sides 
passing gradually into white from the darker colors of the back. The pectoral, ventral, and 
anal fins are bright red, the former having a tinge of yellow, and the dorsal and tail fins are 
brownish-red. 
Closely allied to the roach is the Dace (. Leuciscus vulgaris), a common and small species 
that inhabits most English streams. The well-known Chub (Leuciscus cephalus ) also belongs 
to this genus, as does the Bleak (Leuciscus alburnus ), in many countries called the Tailor 
Blay by the ignorant, from the idea that whenever any other fish, especially the pike, wounds 
its skin, it immediately seeks the aid of the Bleak, which, . by rubbing its body against the 
wound, causes the torn skin to close. The beautifully white crystalline deposit beneath the 
scales was much used in the manufacture of artificial pearls, hollow glass beads being washed 
in the interior with a thin layer of this substance, and then filled with white wax. The scales 
of the white-bait were also used for the same purpose. The Minnow (Leuciscus phoxinus ) is 
another member of this large genus, and is too well known to need description. 
We now come to another family, selecting as an example a tolerably well-known species. 
The Sly Silurus, sometimes called the Sheat-fish, is found in many rivers in different 
parts of the world. 
As may be seen by the engraving, it is a curious-looking fish, and is easily recognizable 
by the six tentacular appendages of its mouth, the two that are situated on the upper lip 
being of very great length. The precise object of these tentacles is not quite clear, though 
some persons believe them to be used as decoys, like the fin rays of the fishing frog, and to 
be enrployed in enticing unwary fish within reach of the mouth. Dr. Gunther has kindly 
informed me, that he has often seen these fishes at liberty in their native streams, and that 
they are capable of directing the points of the tentacles towards any object that they seem 
anxious to examine. It is, therefore, probable, that these curious appendages are employed 
as organs of touch. It is one of the mud-loving fishes, and has a custom of hiding itself in 
holes, or nearly burying itself in the soft alluvium of the river’s bed. 
The flesh of the Silurus is not held in very high estimation, although its flavor is good ; 
for it is so fat and gelatinous, that it is difficult of digestion, and not to be eaten by persons 
of small assimilative powers. A kind of coarse isinglass, or very fine glue, is made from the 
swimming-bladder of this fish. The eggs of the Silurus are not very numerous, in proportion 
to the size of the adult fish, and are of a greenish color. They are much eaten by the 
various fish. 
The color is dark green above the lateral line, and of a paler tint below it, and a number 
of spots are scattered over the body without any apparent arrangement, The” abdomen is of 
a yellowish color, and the fins are tinted with blue and yellow. The Silurus sometimes 
reaches a considerable size, specimens of seven feet in length and weighing from seventy to 
eighty pounds having been captured. 
\ 
PLECTOGN ATHI. 
A very curious order of fishes now comes before our notice. These creatures are called 
Plectognathi, because their jaws are coalescent. 
The remarkable family of the Trunk-fishes, or Sclerodermi, are known by the curious 
structure of the external surface, which is composed of a series of hard scales forming a con- 
tinuous bony armor, 
