FORM AND LOCOMOTION 15 



(Carcharinus) possess slender, perfectly streamlined bodies, 

 conical heads, pointed snouts, and powerful muscular tails 

 (Figs. 23c; 82 a) ; the Carpet Sharks {Orectolobus) have stout 

 thick-set bodies, considerably flattened from above downwards, 

 massive heads, broadly rounded snouts, wide mouths, and 

 much reduced tails with comparatively small dorsal fins 

 (Fig. 82b) ; the Rays (Raiidae) have very broad, flat bodies, the 

 head, trunk and enormously expanded pectoral fins being 

 completely welded together to form a circular or quadrangular 

 disc, from which the feeble tail with its tiny dorsal fins projects 

 as a slender appendage (Figs. 8a; 14B). The Blue Shark is an 

 inhabitant of the open sea, feeding almost exclusively on other 

 fishes which it chases with great vigour; it is essentially a strong, 

 speedy fish, every line of its body intended for rapid progress 

 in pursuit of prey. The Carpet Shark, on the other hand, 

 relies on cunning rather than speed to obtain a meal, lying 

 in wait on the sea floor until the prey comes within reach of 

 its jaws. The loss of swimming power is here compensated for 

 by the remarkable manner in which the Shark resembles its 

 surroundings, its appearance when at rest being that of a 

 weed-covered rock (cf. p. 216). The uniform steely blue 

 coloration of the Blue Shark is replaced by a beautiful variegated 

 pattern which harmonises closely with the sea bottom. The 

 Ray is another sluggish, ground-living fish, and also depends 

 to a large extent on its general resemblance to the surroundings 

 to escape observation by enemies. Its flattened form is ad- 

 mirably adapted for this particular mode of life, but, as will 

 be seen later, its unusual method of locomotion enables this 

 fish to move with much greater rapidity than would appear 

 possible from its appearance. Some still more specialised 

 members of this order have acquired other protective devices 

 in addition to their coloration, as, for example, the Torpedo 

 or Cramp-fish (Torpedo) with its powerful electric organs 

 (Fig. 61), and the Sting-ray (Trygon) with one or more strong, 

 saw-edged and poisonous spines on its tail (Figs. 32B; 36E). 



A body flattened from above downward is generally spoken 

 of as "depressed," while that which is flattened from side to 

 side is "compressed." Among Bony Fishes the former type is 

 very rare, but the well-known Angler-fish or Fishing-frog 

 (Lophius), in which mimetic resemblance and cunning in 

 obtaining a meal has been brought to a pitch of perfection 

 (Fig. 89) and the Httle Bat-fish (Ogcocephalus) , with the upper 

 surface of its body protected by a covering of hard bony warts 



