Page:Popular Science Monthly Volume 6.djvu/180

168 dental ribbon, the broadly-spread pedal disk hides it, the exact method of the operation is concealed. Having with the utmost care witnessed a number of times the creature in the burglarious act, I give the following as my view of the case: With its fleshy disk, called the foot, it secures by adhesion a firm hold on the upper part of the oyster's shell. The dental ribbon is next brought to a curve, and one point of this curve on its convex side is brought to bear directly on the desired spot. At this point the teeth are set perpendicularly, and the curve, resting at this point as on a drill, is made to rotate one circle, or nearly so, when the rotation is reversed; and so the movements are alternated, until, after long and patient labor, a perforation is accomplished. This alternating movement, I think, must act favorably on the teeth, tending to keep them sharp. To understand the precise movement, let the reader crook his forefinger, and, inserting the knuckle in the palm of the opposite hand, give to it, by the action of the wrist, the sort of rotation described. The hole thus effected by the drill is hardly so much as a line in diameter. It is very neatly countersunk. The hole finished, the little burglar inserts its siphon or sucking-tube, and thus feeds upon the occupant of the house into which it has effected a forced entrance. To a mechanic's eye there is something positively beautiful in the symmetry of the bore thus effected—it is so "true;" he could not do it better himself, even with his superior tools and intelligence.

Oystermen also complain of ravages perpetrated by the great conch. But there are two of these conchs, widely distinguished by naturalists. One of them has the upper edge of the whirls ornamented with a projection, with bosses at uniform intervals: this is the keeled conch, and is called, by Conrad, Fulgur carica. The other one has a canal or groove running round the shell, on the top of the whirls: this is the grooved conch, and it has lately been named, by Gill, Sycotypus canaliculatus. The oystermen say that these conchs "rasp the nib of the oysters;" and with their large tongue-files this is not hard to do. It is certainly going a great way for an analogous case; but I have examined numbers of the first-created oysters, fossil oysters, in the New Jersey Cretaceous formation, and have found not a few among them which had received precisely that treatment from certain ancient carnivorous gasteropods.

But the most insidious foe to the life and peace of the poor oyster is the star-fish. The American species, which does the mischief, is the green star-fish (Asterias arenicola). The species obnoxious to the European oyster is the red star-fish (Asterias rubens). (See Fig. 10.) The sea-star does not like water that is too brackish; that is, it loves saltwater. Whenever the Shrewsbury River is affected by the breaking in of the sea, there is danger for its celebrated oysters. On several occasions, at such times, the star-fishes have come up in great numbers, and utterly destroyed the bivalves. At one time so great were