30 THE ANGLER-NATUEALIST. 



1. represents the pre-operculum, or fore gill-cover. 



2. The operculum, or gill-cover proper. 



3. The sub-operculum, or under gill-cover. 



4. The inter-operculum, or intermediate gill-cover, and 



5. The branchiostegous rays, or gill-rays. 



The gill- covers, it will thus be seen, consist of four pieces 

 each : the pre-operculum, or fore gill -cover, 1 ; the oper- 

 culum, or gill-cover proper, 2; the sub-operculum, or 

 under gill-cover, 3 ; and the inter -operculum, or inter- 

 mediate gill-cover, 4. The three last of these are articu- 

 lated, or jointed on, to the temporal bone (i in head of 

 Perch), and play upon the pre-operculum (a fixed bone), 1 ; 

 and by the opening and shutting of these gill-covers respi- 

 ration is carried on. When a line or division is observable 

 anterior to, or in front of, the fore gill-cover, it marks the 

 boundary of the cheek. 



The branchiostegous* rays, or gill-rays, marked 5, form 

 a bony fan-like appendage, or fringe, to the lower margin of 

 the gill- covers, to which they are attached. 



* Branchiostegous rays from the Greek branchia, gills, and stegein, 

 to cover. 



