BUEROWING MOLLUSKS. 117 



aoh may be the means through which the tunneling is conducted, 

 and that instead of being employed as food within the body it is 

 poured out upon the stone, so as to dissolve it, the softened sub- 

 stance being then removed by the foot. The Boring Snails do 

 not congregate together during hibernation, as is the well-known 

 custom of the garden species, but are always solitary. Sometimes 

 two or even three are found in the same burrow, but then they 

 are always at some distance from each other, and form supple- 

 mentary tunnels of their own. In my own specimen there is a 

 curious example of this peculiarity, where the snail has contrived 

 to bore completely through the barrier that separates it from a 

 neighboring tunnel, and has made a hole as large as the key-hole 

 of an ordinary writing-desk, and nearly of the same shape. 



There are many marine-boring mollusks, some of which exca- 

 vate mud, others stone, and others timber. Of the mud-borers I 

 have little to say, few of them possessing points worthy of notice. 

 Perhaps the most noteworthy of these is the common Gaper 

 Shell {Mya arenaria), so called because one end of the shell 

 gapes widely, in order to permit the passage of a long and stout 

 tube. In a specimen now before me, the tube is between three 

 and four inches in length, and at the base is large enough to ad- 

 mit the thumb. As, however, it gradually tapers to the extremi- 

 ty, the aperture at the other end is scarcely capable of receiving 

 the little finger. The walls of this tube are very thin and mem- 

 branous, and it is more or less retractile, carrying within it the 

 siphons through which the moUusk respires and takes nourish- 

 ment. 



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 mollusk, 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 through 

 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, glycerin, or other antiseptic liquid. The Gaper 

 Shell is esteemed as an article of food by man, beast and bird ; 



