STURGEONS. 151 



endued with considerable powers of feelings and taste; in which 

 sensations they are aided by the barbs which hang from the 

 under surflice of the snout. The fifth, or infraorbital jjair of 

 nerves, which are particularly the organs by which sensation 

 or feeling is distributed, is furnished to the snout and barbs; 

 while the facial branch of the nerve of hearing proceeds to 

 the integuments of the mouth and lips, and also to the gill- 

 covers, thus offering no slight support to the opinion that 

 Sturgeons are susceptible of the influence of sounds, as well 

 as of other acute sensations. 



In the nostrils also these fishes differ from the Sharks and 

 Skates, by having them placed above the snout, and in front 

 of the eyes, where it is usual to find them in the fishes 

 characterized by the usual bony skeleton. The form of the 

 body, and especially of the tail, approaches to that of the 

 Sharks; but the resemblance of the latter becomes less on 

 close inspection; for although the lobes are unequal, and the 

 vertebral column is continued along the upper lobe to the end, 

 the fin itself is distinctly supported by branched rays, as in 

 many of the fishes belonging to other tribes. The general 

 texture of the skin bears a near resemblance to what is found 

 in Skates, being soft, and thickly covered with mucous jiores; 

 but the bony plates on the sides and head possess a texture 

 and use which differ from what is generally found in plagi- 

 ostomous fishes, and cause this family to display a closer 

 approach to a class which INIons. Agassiz has denominated the 

 Placoid race; of which a large proportion is only found fossil, 

 but of which one of the distinguishing characters is that they 

 have on their bodies a defence of plates, shields, or scales, 

 which are covered with a thick and firm coat of enamel. 

 These plates are arranged in lines lengthwise on the body, 

 and on the head and cheeks arc flattened into shields; closely 

 pressed together, in something like regular order, but without 

 that strict orderly arrangement, at least along the middle line 

 of the head and snout, which has been claimed for them, and 

 by which it has been supposed some sejDarate species might be 

 defined. 



Professor Owen supposes that the intention of this sj^ecial 

 armature on the head and body is chiefly for protection in 

 the situations which these fishes frequent. They were designed, 

 he says, to be the scavengers of the great rivers; they swim 



