INSTRUCTION. 9 
latter term on account of its suggestiveness ; d is the anal 
fin, for which the writer can ofler no English substitute; 
c are the two ventrals or belly fins ; b is the pectoral or 
shoulder fin, having a com23lemental one on the other 
side of the fish ; and a represents what in learned lan- 
guage are called hranchiostegous rays, a name that, 
being translated, means merely gill-rays. What is not 
in a name ! h is the lateral line. Then bearing in mind 
the great divisions of soft and hard finned, the subdi- 
visions are distinguished by the fish having the ventrals 
behind the pectorals and on the abdomen, giving them 
the name of abdominal fish, or before the pectorals, 
giving rise to the name jugular or throat finned, and 
below the pectorals, giving the name thoracic or shoulder- 
finned fish. Philosophers pay little attention to the 
dorsal and anal fins, and fish, without losing their iden- 
tity, can have as many as they please. In caudals, 
unlike human Caudles, they are restricted to one. There 
are other fish, such as eels, denominated apodal or/ootless, 
because the lower fins or feet are wholly wanting. 
After having examined the texture, number and loca- 
tion of the fins, and counted the number of the rays in 
each, the naturalist next turns his attention to the hard 
bony portion of the head, Avhich covers the gills, and opens 
and shuts as the fish breathes, and which, with the excel- 
lent common sense for which naturalists are notorious, 
he calls the operculum. It is divided into the operculum, 
or gill-cover proper, 'No. 1 ; the pre-operculum, or fore 
gill-cover, No. 2 ; the inter-operculum, or middle gill- 
cover, N'o. 3 ; and the sub-operculum, or under gill-cover, 
No. 4. The head, in the foregoing diagram, is intended 
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