72 A HISTORY OF FISHES 



In some fishes, of which the John Dory {Zeus) and the 

 Horse Mackerel {Trachurus) may be mentioned, the spinous 

 portion IS separated off from the remainder as a distinct fin 

 (Fig. 4 IB). In the Cod {Gadus) and related species the anal fin 

 IS dnided into two portions, each being composed entirely of 

 soft rays (Fig. 28b). In many of the South American Cyprino- 

 donts [Poeciliinae), tiny fishes inhabiting fresh and brackish 



Fig. 31. — CERATIOID ANGLER-FISHES. 



A. Linophryne arborifer,X i ; b. Melanocetus johnsoni^X^ ; c. Lasiognathus 



saccostoma, X i . 



waters, the males are much smaller than the females, and the 

 anal fin is specially modified to form an organ of elaborate 

 structure used for purposes of copulation (cf. p. 296). 



The last of the median fins, the caudal, has already been 

 mentioned in discussing the tail itself, and Httle need be added 

 here. Like the dorsal and anal, it is composed of simple or 

 branched rays supporting a thin membrane; true spines are 

 never developed in this fin, but rudimentary or procurrent rays 



