180 MAMMALIA, REPTILIA, ETC. 



in some of the Australian rivers. In the early liassic 

 period these Australian fishes lived in British estuaries, 

 as is proved by the occurrence of their teeth in the 

 Rhaetic beds of Gloucestershire and elsewhere. The 

 Brighton mud-fish is nearly related to them, although 

 a native of African streams. It possesses both rudi- 

 mentary lungs and gills, whilst its elementary limbs 

 can hardly be distinguished as legs or fins. 



The most interesting of aquarium fishes, however, 

 are undoubtedly those belonging to the shark family. 

 Few of them are eaten as food, but many of them are 

 more or less familiar to the reading public. No fishes 

 have more graceful motions in the water, on account 

 of the ease with which their unequally lobed tails 

 enable them to turn over and round about. They are 

 very active, especially at night, when they are liable to 

 hurt themselves against the rockwork, unless some 

 such ingenious arrangement of dimly lighting the 

 water be adopted as we have already quoted from Mr. 

 Saville-Kent. The most familiar of the fishes of this 

 class which are kept at Brighton, the Crystal Palace, 

 and elsewhere are the smooth hound, or skate-toothed, 

 shark (Mustulus vulgaris). The tope (Galeus cants], 

 also called the " miller's dog," has been so far tamed 

 as to bring forth "litters" at Brighton, and the 

 young (as is usual in some fishes of this class) were 

 brought forth alive and not as eggs. The largest 

 individuals of this fish, which is nearly as rapacious, 

 although not so abundant, as the common dog-fish 



