184 MAMMALIA, REPTILIA, ETC. 



spotted, they are natives of deep water, and therefore 

 require a deep tank. Perhaps this is on account of 

 their nocturnal habits, as they hide away from the 

 light in the deep parts where it cannot penetrate, 

 and are all more or less surface swimmers by night. 

 In aquaria they are fond of taking shelter in such 

 nooks and crannies as the rockwork may have pro- 

 vided for them. Sometimes they are seen lazily 

 reclining on the shingly bottom, with their bird-like 

 eye-membranes closed, but the practical announcement 

 of "meal time" is sufficient to rouse them into a state of 

 activity only excelled by a batch of hungry carnivorous 

 animals in a menagerie, to whose lithe and supple 

 motions, those of the " ground sharks " or dog-fishes 

 might be compared. 



The fact that the latter fishes bring forth their 

 young in egg-cases, and not alive, as the sharks do, 

 and the resemblance of these egg-cases to those of the 

 rays, shows us that the two groups are nearly related. 

 Perhaps one of the " connecting links " is the angel, 

 or angel fish (Rhina squatina) ; although why the 

 popular name should be so easily convertible is not 

 apparent. There is undoubtedly a strong resemblance 

 between the rounded head and broad-spread pectoral 

 fins of this fish and the hooded cowl of a monk. This 

 fish is tolerably common in the Irish Sea, where it is 

 shunned by the fishermen on account of its habit of 

 simulating death, and snapping at them when least 

 expected. Like many others of its class it is noctur- 



