THE RAZOR SHELL. 123 



of unfrequent occurrence that one of the creatures hits upon the 

 burrow of another, and if it does so, it will not, and in fact can 

 not, alter the direction of its tunnel. Neither is it able to wait 

 until the other shell has burrowed farther, but eats its way silent- 

 ly and unrelentingly along, cutting through the shell and body 

 of its luckless companion, and thus bringing on it a violent death, 

 which its rocky home seems especially intended to avert. The 

 hole is on the average about five or six inches in depth, and the 

 animal does not lie free in its burrow, but attaches itself to the 

 side by means of a byssus or cable, like that of the mussel, save 

 that it is smaller, because the strain upon it is not so great as 

 when the shell is anchored in the open sea. This shell has a very 

 wide range of locality, and is sometimes found at a very great 

 depth, specimens having been procured at a depth of nearly 900 

 feet. It attains its largest dimensions in the colder seas. 



Another member of this family {Xylophaga dorsalis) burrows, 

 as its name implies, into wood and not into stone. It is a small 

 species, and of a very globular form, and never burrows to any 

 great depth, an inch being the ordinary length of its tunnel. The 

 shells of this creature are often found in floating wood, or in the 

 sea-covered portions of wooden piles, and it is a notable fact that 

 the burrows are always made across the grain of the timber in 

 which it lives. 



Those who are fond of wandering on the sea-shore, will often 

 have experienced tangible proofs of the existence of another bur- 

 rowing mollusk, the Eazor Shell (Solen ensis). 



In some parts of our coast it is impossible to walk on the mixed 

 rock and sand, when the tide has receded, without noticing innu- 

 merable jets of water, which start from the ground without any 

 perceptible cause, leap for a foot or so in the air, and then disap- 

 pear. On watching one of these miniature fountains, and looking 

 at the exact spot whence' it proceeds, two little round holes are 

 generally seen in the sand, so close to each other as to resemble a 

 key-hole, and large enough to receive an ordinary goose-quill. If 

 the finger be placed on the spot, or even if the foot descends heav- 

 ily on the ground, the curious object vanishes far out of the reach 

 of a probing finger. The jets are thrown up by the Solen, and 

 the two little holes are the open extremities of the siphon, that 

 wonderful instrument through which the creature obtains its 

 nourishment. 



