I. Venus plicata. (Gmel.) II. Venus puerpera. (Linn.)
III. Venus reticulata. (Linn.) IV. Venus Gnidia. (Broderip.)
V. Cytherea zonaria. (Lamarck.)
VI. Cytherea petechialis. (Lamarck.)
VII. Cytherea maculata. (Linn.)
In C. hians (Fig. 144), the mantle has a large opening in front, fringed anteriorly with papillæ in the form of tentacula; the inhabitant of the shell has a very large foot, with a bend or knee near the middle; its mouth is transverse and funnel-shaped, and furnished with a triangular appendage. One of the peculiarities in the organization of these molluscs is its direct connection with their mode of life. In short, these molluscs, which most commonly live on the sea shore, and bury themselves in the sand to the depth of four or five inches, are enabled to breathe, to draw water for their nourishment, and also to throw off the products of digestion, by having the mantle prolonged into two tubes, the orifices of which reach to the surface of the soil. By means of these feet and an extremely curious organ of locomotion, the Cardiums can at will issue from their holes and re-enter them. The fishermen of the shore easily recognize the presence of these animals by the little jets of water which they throw up through the sands.
Fig. 144. Cardium hians (Brocchi).
Fig. 145. Cardium Greenlandicum (Chemnitz).
Fig. 146. Cardium aculeatum (Linnæus).
Fig. 147. Cardium edulis (Linnæus).