24 NATURALIST'S CABINET. 



Peculiar habits. 



some only a canal, as in the cod, salmon, ling, 

 &c. and in others a pretty large cavity, as in the 

 ray kind. In the jack there is an oblong bag, 

 or blind process,* which is an addition to those 

 canals, and which communicates with them at 

 their union. In the cod, &c. that union of the 

 three tubes stands upon an oval cavity, and in 

 the jack there are two of those cavities; these 

 additional cavities in these fish appear to answer 

 the same purpose with the cavity in the ray or 

 cartilaginous fish, which is the union of the three 



canals. 



" The whole is composed of a kind of cartila- 

 ginous substance, very hard or firm in some 

 parts, and which in some fish is crusted over 

 with a thin bo-w lamella, so as not to allow them 

 to collapse: for as the shell does not form any 

 part of these canals or cavities, they must be 

 composed of such substance as is capable of 

 keeping its form. 



" Each tube describes more than a semicircle. 

 This resembles in some respect what we find in 

 most animals, but differs in the parts being dis- 

 tinct from the skull. 



" Two of the semicircular canals are similar 

 to one another, may be called a pair, and arc 

 placed perpendicularly; the third is not so long; 

 in some it is placed horizontally, uniting as it 

 vere the other two at their ends or terminations. 

 In the skate it is something different, being only 

 united in one of the perpendiculars. 



