320 FISHES. 



plainly to enunciate, may be given as follows: A verte- 

 brate animal that lives in water, breathes the dissolved air 

 by means of gills, and swims by the aid of fins. 



In tlie ma J rit y of cases > tlie bod y is covered 

 with scales; in some, however, as the tench 



and eel, these are minute and embedded ; in others, as the 

 conger, they are absent. It will now be desirable to con- 

 sider briefly some of the chief external characters of fishes. 

 Though not sufficient in themselves to distinguish them 

 from the class of reptiles, among the most characteristic of 

 these are the scales, which are, as above men- 

 tioned, sometimes small and embedded in the 

 skin, sometimes absent and replaced by an arrangement of 

 calcified processes like teeth, as in sharks, in which order we 

 find the skin similar within the mouth. In the sturgeons 

 we find rows of plates along the body. These scales have 

 been denominated according to their form, as ctenoid, those 

 with serrated edges ; cycloid, in which the edge is smooth. 

 (See figures in Taylor's ' Half-Hours in the Green Lanes,' 

 cap. ii.) 



The shape of fishes is subject to considerable variation, 

 for in addition to the typical tapering, torpedo 

 ( form > we find the bod } T flattened > laterally, as 



in the flat-fish ; vertically, as in the rays and 

 skates ; elongated, as in eels ; spherical, as in sunfish. 



The organs of locomotion, or fins, are vertical (lying 

 along the back and belly) and unpaired, or horizontal 

 (lying on the sides) and paired. The vertical 

 fins are called, according to their position, 

 dorsal (along the back), anal (on the belly, just before the 

 tail), or caudal (the tail-fin); the paired fins are the 

 pectoral (behind the gill-covers) and ventral (or pelvic, 

 beneath the last), the latter being either abdominal (im- 

 mediately beneath the pectorals), thoracic {behind and be- 

 neath the pectorals), or jugular (before and beneath the 

 pectorals). The dorsal fins are either soft or spinous, in- 

 termittent or continuous, the salmon and its kind having, 



