26 



TOP. 



off — the owner being, of course, previously 

 killed. 



When this organ is properly displayed, it will 

 appear furnished with one array of teeth, very 

 minute, but very strong, and quite adequate to 

 the work which they have to perform. In fact, 

 the tongue is a miniature file, and is used not 

 so much for tasting the food, as for a rasp, where- 

 with to cut it off. The top, therefore, is an useful 

 inhabitant of an aquarium, for he saves an im- 

 mensity of trouble in keeping the glass sides 

 clean. After an aquarium has fairly settled 

 itself, the algse pour out their spores, and these, 

 adhering to the glass, there affix themselves, so 

 that in a few weeks the glass becomes dimmed 

 by the mass of minute vegetation. Here the 

 tops and periwinkles come to our aid, and by 

 means of the natural scythes with which they 

 are armed, soon mow away the greater part of 

 this vegetable growth. They seem to do their 

 work as composedly and regularly as if they were 

 paid by the day for it. The Livid Top may be 

 found alive among the rocks at low water. 



I have already stated that the periwinkles are 

 useful inhabitants of an aquarium, and such is 

 the case as long as they can be kept alive. But 

 they are often very perverse in disposition, and 



