84 LOWER VERTEBRATES. 



The Squatinid^;, or angel-sliarks, embraces forms whicli closely approximate the 

 rays in appearance. They have a flattened body, with very large pectoral fins, which 

 project fur out on either side, giving the whole a rhomboidal appearance ; behind the 

 pectorals are two dorsal fins ; the moutli is at the end of the head, and the lateral gill- 

 clefts are partially concealed by the base of the pectoral fin. 



The angel-fish or monk-fish, Squatina angelus (or Rliina squatind), is found in 

 almost all the temperate and tropical seas. It grows to a lengtli of about fi^-e feet, 

 and frequents the bottom, where it feeds upon fishes, rays, and the like. It is remark- 

 ably voracious. It brings forth its young alive, sometimes to the number of twenty 

 at a birth. The time of reproduction is not settled ; some say it is in the sjjring, 

 others in the fall ; both may be true. The name angel-fish is only appropriate if we 

 regard the pectoral fins as wings ; in all other respects the appearance is anything but 

 angelic. 



Order II. — EAI^. 



As was said on a previous page, when ti-eating of the sharks, the only prominent 

 constant character separating the sharks and skates was to be found in the position 

 of the gill-clefts ; lateral in the one, ventral in the other. Besides this, however, there 

 are several others which are more or less constant, and really of more importance than 

 this one. Among these we may mention tlie flattened, depressed body, from which 

 the broad, expanded pectoral fins are scarcely distinct, while the tail is usually long 

 and slender, and appears as an appendage, rather than an integral part of the whole. 

 There are no anal fins, and the dorsals, when present, are confined to the tail. The 

 skeleton of the pectoral fins is united to the skull by cartilage, and the median arti- 

 cular facet between the skull and the first vertebrte is lacking. 



So far as is known, all of the rays are carnivorous, but onl)- the shark-like forms 

 (saw-fishes and the Rhinobatidae) actively pursue their prey. These forms are strong 

 and rapid swimmers, but the true rays live on the bottom, and swim solely by the un- 

 dulations of the edges of the pectoral fins, as is sliown in the upper figure of Maia 

 batis, on page 86. These must perforce live on shell-fish, crabs, flounders, and other 

 forms that frequent tlie bottom, and for this the mouth is Avell fitted. It is placed on 

 the ventral surface, so that, were it not for a capacity of movement of the jaws, it 

 could not readily take its prey The ray swims rapidly over a fish, and then settles 

 down upon it, holding it from escape with its broad body; then, by suitable muscles, 

 the jaws are protruded beyond the rest of the surface, and the object is taken in. 

 The statement often made, that the prey is not directly seized l^y the jaws, is not cor- 

 rect of some — if, indeed, of any — of the species. The difiiculty of observing their 

 eating habits has caused the mistake. 



According to Dr. Gtinther, the rays do not frequent deep waters, only one having 

 been known to occur in water over a hundred fathoms in depth. This exception was 

 said to have been dredged in 565 fathoms by the 'Challenger' expedition. About one 

 hundred and fifty species are known, but none of these have a geographical range to 

 compare with that of many sharks. They are more restricted, and almost all of them 

 may be considered shore forms, only the eagle rays being found far from land. The 

 rays are not confined to salt water, but several forms, esjiecially in South America, 

 occur in fresh water far inland. 



Most of the species are usually said to be ovi]iarous, but, according to Dr. Gill, 

 about three quarters of the known species bring forth their j'oung alive. The eggs 



