68 AMMODYTIDJE. SILURID.E. 



are wanting, are generally of an elongated form, somewhat re- 

 sembling that of the Eels, with which indeed they were arranged 

 by Cuvier. They may be readily distinguished from the Eels, 

 however, by the freedom of their opercula ; these in the Eels are 

 confined by the skin in such a way as only to leave a small aper- 

 ture. In the AMMODYTIDJE, or Sand-lances, the caudal fin is 

 distinct and forked ; and the skin, which is naked, is of a beauti- 

 ful silvery lustre. They are small Fishes which frequent our 

 coasts, burying themselves in the sand to a depth of six or seven 

 inches during the time that it is left dry by the ebb tide. They 

 are used as baits by the fishermen, who drag them out of the 

 sand by means of iron hooks and rakes. The OPHIDIID^E are 

 still more Eel-like in their appearance ; their perpendicular fins 

 forming a continuous border round the posterior extremity of the 

 body. They are sometimes destitute of pectoral fins. Two or 

 three species have been taken on the British coasts, but most of 

 them inhabit the Mediterranean ; none attain a large size. 



F. PHYSOSTOMI. 



630. In this, the last group of the Bony Fishes, the air-blad- 

 der is connected with the pharynx by a sort of duct, a character 

 which only occurs elsewhere amongst the Ganoidei. Their fins 

 are always supported by soft rays, but in some cases the first ray 

 of the dorsal, anal, and pectoral fins is spinous. The ventral fins, 

 when present, are always situated on the abdomen. This group 

 includes nearly the. whole of our fresh-water Fish, and an im- 

 mense number of species which inhabit the seas ; some of the 

 latter are of the highest importance to Man. 



63 1 . The first family is that of the SILURID^E, or the Silures, 

 distinguished by the want of scales ; the skin is naked, but fre- 

 quently has bony plates imbedded in it. The mouth is surround- 

 ed by tentacles ; the first ray of the pectoral fin is very strong 

 and bony, and the Fish can, at pleasure, lay it flat on the body, 

 or keep it fixed in a perpendicular direction, in which case it 

 becomes a formidable weapon, capable of inflicting very trouble- 



