FINS 79 



Flying-fishes. Among other fishes capable of short and generally 

 erratic flights, the little Chisel-jaw {Pantodon) of African rivers 

 and swamps, and a peculiar deep-bodied Characin fish from 

 South America [Gasteropelecus) may be mentioned. The pectoral 

 fins of the Chisel-jaw are not particularly long, but are joined 

 to the body by flaps of skin. 



The little Mud-skipper {Periophthalmus) , found on the coasts 

 of tropical Africa, Asia, and AustraHa, is renowned for its habit 

 of leaving the water and walking or skipping about on the 

 sand or mud in search of food. It chases its insect prey among 

 weeds and rocks, and on land is quite as agile as many lizards. 

 The pectoral fins are specially modified in relation to this 

 habit, each being attached at the end of a kind of muscular 

 arm, which can be moved backwards and forwards and is 

 used exactly like a limb. Among other structural peculiarities 

 designed to assist its progression on land, the low anal fin and 

 the stout lower rays of the caudal may be noticed (Fig. 34f). 

 Dr. Regan writes: "When walking on the mud each step is 

 accomplished by a forward movement of both pectoral fins, 

 which are then put on the ground and draw the rest of the 

 body after them; these steps are repeated rapidly, and as each 

 results in an advance of about half an inch, very fair progress 

 is made; the pelvic fins support the body during the turning 

 forward of the pectorals. But, as their name implies, the Mud- 

 skippers often leap along the mud, or from one stone to another; 

 short jumps may be accomplished by the action of the pectoral 

 fins alone, but longer ones, which may be as much as a yard 

 long, are made by a stroke of the tail. This is their way of 

 getting along when they are in a hurry, and they may often be 

 seen playing on the mud, jumping about in chase of each other." 

 In the Sea Toads (Chaunacidae) and Frog-fishes [Antennariidae) 

 these fins again take the form of arms, ending in many fingered 

 "hands," by means of which they are able to crawl slowly 

 about on the sea floor or to hang on to rocks or weeds (Fig. 85). 

 In the related Bat-fishes {Ogcocephalus) the "arms" are even 

 more muscular (Fig. 40D). 



In certain fishes some or all of the rays of the pectoral fins 

 may be drawn out into delicate filaments which serve as 

 organs of touch. In the Thread-fins {Polynemus) , for exam.ple, 

 some four to eight of the lower rays are detached from the rest 

 of the fin, and take the form of hair-like structures which may 

 be longer than the fish itself (Fig. 34d). In a deep-sea fish 

 known as Bathypterois the eyes are very much reduced in size, 



