"4th Family, Myaria.
| Mya | Mya, or gaper. |
| Anatina | Mya. |
"The animal of Mya has also a foot: it buries itself in the sand. You know the broad tooth of the Mya genus. Anatina has a tooth on each valve.
"Second Section contains four families.
"Mactracea has the following genera:
| Lutraria | Mactra. |
| Mactra | Mactra. |
| Crassatella | Mactra. |
| Erycina | —— |
| Ungulina | —— |
| Solenomya | Mya. |
| Amphidesma | Tellìna. |
"Crassatella is a genus from the seas of New Holland. The shell is very thick, with a brown epidermis. A fossil species is found at Hordwell cliff. There are several species also found in the chalk. Mactra, Lutraria, and Erycina are found in a fossil state. Crassatella sulcata is common in London clay.