RAYS. 107 



terranean, it has been found occasionally on 'the south coast of 

 England. 



The family oiRhinida contains only one species, the "Angel-fish" 

 or " Monk-fish " (Rhina squatina) (Case 41), which approaches the 

 Rays as regards form and habits. Within the temperate and tropical 

 zones it is almost cosmopolitan ; it does not exceed a length 

 of five feet ; it is viviparous, producing about twenty young at 

 a birth. 



The Pristiophorida (Case 41) resemble so much the common 

 Saw-fishes as to be easily confounded with them, but their gill- 

 openings are lateral, and not inferior. They are also much smaller 

 in size, and a pair of long tentacles are inserted at the lower side 

 of the saw. The four species known occur in the Australian and 

 Japanese seas. 



B. Batoidei : Rays. 



The true Rays lead a sedentary life, moving slowly on the 

 bottom, rarely ascending to the surface. They progress solely 

 by means of the pectoral fins, the broad and thin margins of 

 which are set in an undulating motion, identical with that of the 

 dorsal and anal fins of the Pleuronectidce, or Flat-fishes. They 

 are exclusively carnivorous, like the Sharks, but unable to pursue 

 and catch rapidly-moving animals. 



The Saw-fishes, Pristida (Case 41), agree with the Rays in the 

 position of their branchial clefts. They are abundant in tropical, less 

 so in subtropical seas. They attain to a considerable size, specimens 

 with a saw 6 feet long and 1 foot broad at the base not being of 

 uncommon occurrence. The saw renders them most dangerous to 

 almost all the other large inhabitants of the ocean. Its skeleton con- 

 sists of three, sometimes five, rarely four, hollow cylindrical tubes, 

 placed side by side, tapering towards the end, andincrusted with an 

 osseous deposit, as shown in a preparation in Table-case C. The 

 teeth of the saw are implanted in deep sockets of the hardened in- 

 tegument, and are, as regards their origin, from dermal papillae, 

 and their mode of attachment a unique structure among Fishes. 

 The teeth proper, with which the jaws are armed, are much too small 

 for inflicting wounds or seizing other animals. Saw-fishes use the 

 saw in tearing pieces of flesh off an animal's body or ripping 

 open its abdomen ; the detached fragments or protruding soft parts 



i 



