SPECIES AND GENERA. 
37 
so on, that can easily be observed. It must not therefore 
be supposed that the points I here notice are in all cases 
the ones with regard to which the classification of the 
fish has been decided. 
It is necessary to know the names of the fins, and 
the signification of the other terms used in these de- 
scriptions. 
By referring to Plate 10 it will be seen that the fin 
on the back of the fish is termed the u Dorsal fin.” 
There may be one or two dorsal fins ; of which the 
hindmost may be an adipose, or gristly fin, without 
rays. 
The fin opposite to the dorsal, on the lower surface 
of the body, is termed the Anal fin. 
The fin at the end of the tail is the Caudal fin. 
(N.B. The tail of a fish is understood to be that part of 
the body between the anal and the caudal fins, it is a 
mistake to call the fin itself the tail). 
These comprise the vertical fins, the remaining fins 
are disposed in pairs, and answer to the four limbs of 
a quadruped. The upper pair are termed the Pectoral 
fins, the lower pair are called the Ventral fins. 
In taking measurement the following rule has been 
observed: — By the “total length” I understand the 
length in a straight line from the end of the snout to 
the base of the caudal fin ; that is to say, the total 
length not including the caudal fin. This affords a 
better standard of comparison, as the fin is frequently 
damaged, or may vary slightly in length, than if the 
fin were included. 
