sri K(ii;()Ns. 151 



endued with consideraLle i)owers of feeling iind taste; in whicli 

 sensations they arc aided by the barbs whieli hang from the 

 under surface of the snout. 'I'he fifth, or infraorbital pair 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 integunacnts of the mouth and lips, and also to the gill- 

 covers, thus offering no slight support to the oi)inion 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 pores; 

 but the bony plates on the sides and head j3ossess 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 Mons. 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 are 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 siipposed some separate species might be 



defined. 



Professor Owen supposes that the intention of this sjiccial 



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 



