"The body is soft, without joints, without head or eyes; it is wrapped in a mantle or tunic. The mouth, always hidden in the tunic, is merely an opening to admit food, without jaws or teeth. The shell is always bivalve; the valves united by a hinge or a ligament; sometimes there are accessory pieces to the valves.
CONCHIFERA.
UNIMUSCULOSA.
"Some of the Conchifera are furnished with a kind of foot, which enables them to move with their shells, to draw out fibres by which they fasten themselves to marine bodies. The muscles that fasten the animals to their shells are thick and strong; their use is, to close the valves by contracting; when the muscle is relaxed, the elastic ligament is sufficient to open them. The Conchifera are all aquatic; some inhabit fresh water, the others dwell in the sea.
"The class contains nineteen families and two orders. The first order, Bimusculosa, contains thirteen families. The first includes genera that you will scarcely expect to find among the bivalve shells.
"1st Family, Tubicolaria, contains,
| Aspergillum, Watering-pot | Serpula. | |
| Clavagella | ——— | |
| Firtuluna | ||
| Septaria | Serpula. | |
| Teredina | Fossil genus. | |
| Teredo | Teredo. |
"Aspergillum Javanum is a rare and curious shell from the Indian seas, ([Plate 9.]) The whole family is remarkable, and was referred, you perceive, to a very different order. Clavagella was till lately considered as existing only in a fossil state. The researches of recent travellers have discovered Clavagella at Port Jackson, in Australia.[A] There is a specimen in the British Museum. The valves are enclosed in the tube.
"The valves of Teredo are noticed as forming part of the Linnæan generic character, you will recollect. Lamarck considers them as true Conchifera. In many specimens of Teredo the valves are wanting, and the tube only remains.
PHOLADARIA.