" SHELL-FISH." IQ7 



organ, in fact, has a double margin, the inner of the two finely 

 fringed, and at its base a row of eye-like beads. 



When prying curiously about the rocks at low-water, under 

 the scrub of weeds and corallines, we are sure to discover 

 little flat pearly shells which we shall almost as surely decide 

 to be young oysters. They are a kind of oyster, though not 

 edible oysters of the genus Ostrea, but Saddle Oysters, of the 

 genus Anomia (/4. ephippium). Although they appear to be 

 firmly cemented to the rock by the lower (right) valve, this is 

 not really so. The thin blade of a penknife gently pushed 

 beneath will move it off with the merest touch, for instead of 

 being fixed by its whole under-surface, it is merely attached 

 by a muscular plug that passes through a comparatively large 

 oval hole in the under shell, near the hinge, and sticks like a 

 sucker to the rock. As it grows older it will probably alter its 

 form, to adapt itself to things it comes in contact with, as its 

 diameter increases. Small specimens, not so large as a three- 

 penny-bit, usually have a colony of much younger individuals 

 located on their upper shell. 



Odd specimens of the Common Mussel (Mytilus edulis) will 

 be found among the roots of weeds on the low-water rocks, 

 but to obtain them in quantity one must go to a mud-bank, as at 

 the mouth of a river ; or they may be found clinging in masses 

 to the wooden piles of piers and breakwaters by means of their 

 byssus-threads. The first thing a mussel does on being placed 

 in an aquarium is to attach itself to the side by this means. 

 Possibly he will wander a little, by means of his foot, to make 

 sure of the right spot upon which to cast anchor, but having 

 settled that point and found that he has made the right choice, 

 there he will remain. 



A mussel is the best of all bivalves for aquarium life. It is 

 true he is not very lively, and does not flit through the water 

 like the young Scallops. He is anchored, and there he stays, 

 simply opening his shell a little way and putting out the 

 frilled edges of his mantle, with their openings for the inward 



