RAYS 69 



in the sand or mud, and the only sign of life is the rhythmical 

 movement of the valve guarding each of the spiracles. But, 

 let a small fish, crustacean or other desirable titbit come 

 within reach, and it at once comes to life, revealing an activity 

 almost incredible in a creature of such clumsy build. The 

 position of the mouth makes it impossible for a Skate at once 

 to seize the prey, but with a swift pounce it literally throws 

 itself upon the unsuspecting victim, holds it down and 

 smothers it with its vast body and fins, and finally grasps it in 

 its jaws. 



The diet of the Skates and Rays is a very varied one, and 

 includes almost every kind of animal life to be found on or 

 near the sea floor. Among outsizes in meals may be mentioned 

 an angler-fish weighing 6 lb. found in the stomach of one 

 individual, and a stone nearly a pound in weight removed 

 from another. 



In almost all Skates and Rays there are more or less marked 

 differences between the sexes, quite apart from the " claspers ", 

 which provide a sure means of sexing all but the very smallest 

 specimens. In some species these differences are so pronounced 

 that the male and female were at one time regarded as distinct 

 forms. In size the females are nearly always larger by about 

 one-third than the males. The number and arrangement of 

 the spines on the upper surface of the disc, and even the 

 shape of the disc itself, differs in the two sexes. All mature 

 males have a patch of curved spines near the edge of each 

 pectoral fin, spines which are entirely lacking in females. It 

 has been suggested that these play some part in holding the 

 female during coition, but it seems more probable that they 

 are offensive weapons, and used in combats between rival 

 males, several of which have been observed to follow a single 

 female and to buffet one another with their pectoral fins. 

 Finally, in certain species the teeth are of a different shape, 

 being pointed in the males and flat in the females. 



A curious feature concerning the eyes of these fishes may be 

 mentioned here, since this probably represents another adapta- 

 tion to their particular mode of life. The upper part of the 

 pupil is covered by a thick dark lobe or veil, rather like a 

 vine leaf in appearance which can be expanded or contracted 

 at will, and thus controls the amount of light that falls upon 



