i 9i 1 



^ore certain and permanent note, upon wliuJk 

 ills fpecific charaders are folely founded : it was 

 ^rft exemplified in the Amphibia Gyllenborgiana^ and 

 he has fince retained it in all his works, fenfiblc 

 however that it is yet liable to failure : this arifes 

 from the number of the fmall Jhields and fcales^ or 

 rings and rug^ of the belly and tail ; and the pro- 

 portion thofe numbers bear to each other in the 

 different fpecies : for example, in our Common 

 Viper the floieUs of the belly are ufually about 146, 

 and the fcales of the tail, that is all below the 

 anus, about 39 or 40 : the Jhields in our Common 

 Snake about 170, and the fcales about 60. 



in the Nantes the fpecific charaders are fliort, 

 but very various in the different genera, as to the 

 parts of the animal from which they are deduced* 

 in the 'Petromyzon and Rata, from the mouthy fins^ 

 teeth, &c. > in the latter vei7 much frpm the bdd^ 

 itfelf : in the Squalus, from a variety of parti- 

 culars : in the Acipenfer, from the cirri or beard, 

 and the dorfal Jhields, or Jquama : in the Balijies^ 

 from the fins and tail : in the OJiracion, from the 

 different angulated form of the body : in the Tetrodon^ 

 from differences in the body chiefly and in the 

 remaining genera, from the form pf the body, an4 

 the differences in the fins. 



Clafs IV. PISCES, Fishes. 



In the earlier editions of the SyJiema Natura^ 

 our author, in the diftribution of Fishes, had 

 followed the method of his friend and fellow 

 collegian yfr/^<^/ j whofe Jcthyologyh^ had publifhed 



^ during 



