will be obtained by supposing it to be made of polished carnelian. This beautiful and versatile foot is suddenly thrust out sideways, to the distance of four inches from the shell. Then, its point being curved backwards, the animal pushes it strongly against any opposing object, by the resistance of which the whole animal, shell and all, makes a considerable step forwards. If the Cockle were on its native sands, the leaps thus made would, doubtless, be more precise in their direction, and much more effective; but, cooped up with its fellows in a deep dish, all these herculean efforts availed only to knock the massive shells against the sides, or roll them irregularly over each other.
It was curious to notice the extent to which the interior of the Cockle was revealed, when the mouth gaped, and the foot was thrust out. By the aid of a candle we could see the interior surfaces of both valves, as it seemed, almost to the very backs. I say, as it seemed, for so thin is the mantle where it lines the shell, and so closely does it adhere to it, that every character of the valves, whether as regards colour or irregularity of surface, was distinctly visible; and thus we were able to distinguish the species, not only by their external marks, but by one character drawn from the interior;—the ribs in tuberculatum extending only half-way across the valves, while in aculeatum they reach back to the beaks.
The former is much the finer species; the valves are more globose, and of a warmer colour; those that I have are even more spinous. The mantle is of a rich deep orange, with elevated ribs, corresponding to those of the valves, of a yellow hue. These ribs of
