INTRODUCTION. 



XIX 



represents one half of this pharyngeal arch of bone, that of 

 the left side, looking from behind, with the teeth in the 

 Carp, Tench, the Roach, and the Barbel. In the Carp, 

 the first on the left hand, the crowns of the teeth are ob- 

 served to be so worn down as to have the appearance of the 

 crowns of the molar teeth in the Hare. In the Tench, the 

 second figure from the left, the structure is less complicated. 

 In the Roach, the form and number again varies ; and in 

 the Barbel, on the extreme right, the teeth are crooked, 

 pointed, and disposed in three regular rows : other fishes 

 belonging to this family have the teeth in four rows, and 

 some in six rows. Considerable diflTerence of form exists in 

 the four examples of teeth here shown ; and a reference to 

 the illustrations of other teeth at pages 98, 103, 106, 113, 

 116, and 248, will show the great variety of teeth that are 

 to be found among fishes, two or more distinct forms of 

 Avhich are sometimes possessed by the same individual. 

 Some further particulars in reference to the teeth will be 

 found in other parts of this work. 



Closely connected with this part of the subject is their 

 food, and. the organs of digestion. 



The food of fishes is very different at different periods of 

 the year, and this may be one of the causes, among others, of 

 the peculiar excellence of the flesh of some species of fishes 

 at particular seasons. 



b 2 



