Page:The Zoologist, 1st series, vol 1 (1843).djvu/115

Rh twice the size of any specimen of E. lividus I met with. Three fine live specimens of E. sphaera (or esculentus of Fleming) were brought in one evening, and being put into a basin of fresh water that their sufferings might be brief, we were surprised to find next morning that their colour was changed;—spines and crust having become a light grass-green.

I had expected to make some interesting additions to my cabinet of shells, but in this I was a good deal disappointed. There are, I doubt not, plenty of Mollusca in deep water, but I saw very few upon the shore. Cockles there are in abundance in the sand, as well as Solen siliqua, S. ensis and Mactra subtruncata.

Rissoa interrupta was common at the roots of the smaller Algae, and Montacuta purpurea, Skenea depressa and Turbo tenebrosus were found nestling at the roots of Lichina pygmaea. I found also imperfect specimens of two rare shells, viz., Pecten nebulosus and Pleurotoma gracilis.

I was however much gratified by finding on the sand at a low state of the tide, about a score of very fine live specimens of Bulla lignaria. Though not uncommon on the Ayrshire coast, I had scarcely ever got it there containing the inhabitant. Every conchologist knows that this Bulla has a calcareous gizzard, of even firmer fabric than the external shell. This gizzard is a wonderful piece of mechanism, which one would not expect to find in the interior of a very soft mollusk. Though I had seen it before, I found that T was but imperfectly acquainted with its structure. I thought it was composed of two plates, but I found that there were three; in this respect resembling the gizzard of the still more delicate Bullaea aperta, though differing considerably in form. Two of the plates are triangular, and placed one above the other, like the upper and nether millstones. They are not quite flat, but a little concave externally and rather convex internally; they are bound together with strong cartilage, and on one of the sides of the triangle there is a third valve or plate, giving strength to the cartilage, and keeping the two grinders at some distance, except at the centre, where the convex points meet, and thus leaving, except at these points, room for the reception of food in the triangular space between the two millstones. The food of the Bulla seems to be the fry of other shell-fish. Though they seem to indulge very freely as to quantity, they appear to be wiser than our biped gourmands, for they keep to one dish. In every one of the specimens I procured the capacious gullet was filled with the fry of Mactra subtruncata. The gullet was in the form of a corn-sack, quite distended, for each contained