FINS 8i 



pro\ided by a fossil Eel ( Urenchelys) from the Chalk of Mount 

 Lebanon which shows distinct traces of having possessed both 

 paired fins as well as a separate caudal fin. Pelvics are absent 

 in all the Pipe-fishes (Syngnathidae) , Symbranchoid Eels {Sym- 

 branchii), Gymnotids {Gymnotiformes) , Globe-fishes {Tetrodontidae) 

 and Porcupine-fishes {Diodontidae) , and are also suppressed in 

 many of the Blennies and Cusk-eels {Blennioidea, Ophidioidea) . 

 E\en when developed, they may be reduced to mere filaments, 

 as in some of the members of the Cod tribe [Gadidae), and in the 

 Oar-fish (Regalecus), where they are represented by a pair of 

 long rays, each expanded into a blade-like structure at the tip 

 (Fig, 8d). In the Sticklebacks [Gasterosteus) each pelvic is 

 composed of a sharply pointed spine and one soft ray (Fig. 

 28f), and in the Pine-cone Fish {Monocentris) (Fig. 42E) and in 

 some of the Trigger-fishes, etc. (Plectognathi) , is reduced to a 

 spine alone (Fig. 42D) . In certain species of File-fishes {Mona- 

 canthidae) the pelvic bone with" its spine is freely movable, and 

 is connected with the body by a wide flap of skin (Fig. loc); 

 this is said to be used by the fish for fixing itself into crevices 

 in the rocks or coral reefs. 



It is very rarely that the pelvic fins have any connection with 

 locomotion, and they mainly function as "bilge keels" or as 

 accessory manoeuvring organs. During rapid swimming they 

 are generally drawn in close to the body. As in the case of the 

 pectorals, some or all of the rays may be drawn out into lengthy 

 filaments, as in the Dwarf Cod-fish [Bregmaceros) and Gourami 

 ( Osphronemus) . 



The most important modification of the pelvics is to form a 

 sucking disc to enable the fish to cling to rocks, stones, and 

 other fixed objects. The little Bornean Sucker {Gastromyzon) , 

 found only in the mountain torrents of Borneo {cf. p. 239), has 

 the whole of the lower surface of the body modified to form a 

 large sucker, in which the long and horizontally placed pectoral 

 and pelvic fins play an important part (Fig. 350). The Gobies 

 (Gobioidea), a large and varied sub-order of fishes, mostly of 

 small size, found mainly am.ong the rocks between tide-marks, 

 have the pelvic fins united to form a rather deep cup-like 

 sucker (Fig. 350). In the Lump-sucker [Cyclopterus) and Sea- 

 snail (Liparis) a somewhat similar sucking disc is developed, 

 but the pelvics have been so much modified as to have com- 

 pletely lost their fin-like appearance (Fig. 35A). This disc is 

 very powerful, and some difficulty is experienced in remo\'ing 

 a fish from an object to which it has attached itself. The Cling- 



