"O. folium is of the second; a curious species, from the Indian and American seas: the shell is fixed to wood and to the roots of trees on the sea-shores.
"Vulsella is a foreign genus, from the Indian and other seas.
PLACUNA.
ANOMIA.
"Placuna does not adhere to any marine substance. The valves are flat, thin, and transparent; the very small space between them shows that the animal must be extremely flattened: there are two singular ribs at the hinge in the form of a V.
"P. placenta, Chinese window-glass, is so transparent when young, that it serves instead of that material in China.
"Anomia. The shells of this genus are fixed, like the oyster, to marine bodies. They live and perish on the spot where they are at first produced. I have noticed the muscle by which they attach themselves. Lamarck informs us that a hard, small operculum is to be seen at the extremity of this muscle, and fills up the hole in the flat valve when the muscle is contracted. ([Plate 5.])
"The family Rudista contains only a few genera, which will be quite uninteresting to you at present.
"The next, Brachiopoda, has
| Crania. | |
| Orbicula | Patella. |
| Terebratula | Some from Anomia. |
| Lingula | Patella." |