nets are merely empty valves thrown ashore by the tide.
There is good reason why this and similar shells should not more frequently be found. As anyone must know who has been accustomed to the dredge or trawl, the black mud in which these shells love to dwell is peculiarly offensive both to the touch and the olfactory nerves. It is sticky and slimy, and will not come off the hand without much difficulty. If the blade of an oar should happen to strike the mud, some of the black, slimy substance is sure to adhere to it, and even after an hour's hard rowing, mud will still be on the oar. "Throw plenty of mud, and some of it is sure to stick," is a well-known proverb, whose force is never thoroughly understood until the various properties of such mud have been practically tested.
Wading in the mud is as disagreeable a process as can well be imagined. Unless the wader be furnished with regular mud-boots, he can wear no covering on his feet; there is not an ordinary boot in existence that will remain on the leg when it is once plunged deeply into the mud. If the wader should dispense with shoes and stockings, he has another disadvantage to overcome, namely, the risk of treading on bits of stick, broken stones, or empty shells, which latter objects have a peculiar knack of lying with their sharp edges uppermost.
No one can judge of the depth to which he may plunge at the next step, and yet he must of necessity keep on the move, or he would sink so deeply that he would run a great risk of being permanently imbedded. Nothing is easier, too, than to lose the balance when mud-wading; and if the wader should happen to lose his perpendicular, down he must subside, the tenacious and treacherous mud preventing him from making the step that would restore his balance. All this time the pressure of the feet forces up quantities of the offensive gases — sulphuretted hydrogen, for example — that have been formed by
