THE GAPER SHELL.— THE LIMPET. 57 



extremity, the aperture at the other end is scarcely capable of 

 receiving the little finger. The walls of this tube are very thin 

 and membranous, and it is more or less retractile, carrying 

 within it the siphons through which the mollusc respires and 

 takes nourishment. 



The Gaper Shell inhabits sandy and muddy shores, and to an 

 inexperienced eye is quite invisible. The shell itself, together 

 with the actual body of the mollusc, is hidden deeply in the 

 mud, seldom less than three inches, and generally eleven or 

 twelve inches from its surface. In this position it would be 

 unable to respire, were it not for the elongating tube, which 

 projects tlirough the mud into the water, and just permits the 

 extremities of the siphons to show themselves, surrounded by 

 the little radiating tentacles which betray them to the experienced 

 shell-hunter. These tentacles or fringes are never seen in the 

 dried specimens, and can only be partially preserved by plunging 

 the animal into spirits of wine, glycerine, or other antiseptic 

 Hquid. The Gaper Shell is esteemed as an article of food by 

 man, beast, and bird ; for not only do human beings dig it up 

 with tools, cook it, and eat it, but the wolves and the arctic fox 

 scratch it out of the mud and eat it raw, and die various sea 

 birds peck it out with their beaks, prize the shell open, and 

 devour the contents. 



The well-known Limpet is a kind of borer, though the holes 

 which it excavates are of very trifling depth, and are probably 

 made by the mechanical friction of the shell and foot against 

 the rock, without any intention on the part of the animal. Those 

 who have been accustomed to wander along the sea-shore must 

 have noticed that the Limpet shells always sink more or less 

 into the rocks on which they cling, and that in very old speci- 

 mens which are covered with algae and barnacles, the shells are 

 often sunk fully half their depth into the solid rock. Grooves, 

 too, of various depths may be seen in the same rock, showing 

 the slow and tedious track which the Limpets have made over 

 its surface, until they finally settled down into some convenient 

 situation. 



