Page:Memoirs of the Geological Survey of Great Britain, Volume 1.djvu/421

408 is not known on the European shores. The range of Mya truncata in depth is much beyond that of Mya arenaria. It inhabits the littoral, laminarian and coralline zones on the coasts of Britain.

Note, Mya truncata appeared in the British Seas during the epoch of the Coralline Crag, and has inhabited their area ever since. During the Glacial epoch it extended its range to the Mediterranean region, where it is now extinct. Sphenia Swainsoni is the young of Mya ovalis, of Turton, the half-grown shell.

, fossil. In situ with both valves united in the Clyde beds.

, recent. Very rare in the British Seas. More frequent in the Arctic Seas of Europe, and those of Boreal America.

Note. Appeared in the British Seas during the epoch of the Red Crag. During the Glacial epoch it extended its range to the Mediterranean region, where it is now found fossil in the Sicilian tertiaries.

8. Mya arenaria, Linnæus.

, fossil. Generally distributed through the British glacial beds. In the mammaliferous crag at Bramerton. [Sweden, Canada].

, recent. The seas of northern and Celtic Europe; of Greenland and of the coasts of Boreal America, as far south as New York.

Note. Appears in the British during the epoch of the Red Crag. It is found fossil in the Campinian beds of Belgium, according to M. Nyst.

9. Mya lata, Sowerby.

, fossil. In the mammaliferous crag of Bramerton.

Note. It is found among the red crag fossils, but it is not known living.

10. Mactra stultorum, Linnæus.

, Mactra magna, Woodward.

, fossil. Mammaliferous crag at Thorp.

, living. Generally distributed through the European Seas, and according to Phillippi, it inhabits the Red Sea.

Note. Appeared in our own area during the Red Crag epoch.

11. Mactra solida, Linnæus.

, Mactra dubia and M. ovalis, Sowerby.

, fossil. General in the sands and clays of the drift. Mammaliferous crag of Thorpe.

, living. All the European Seas.

Note. Occurs in both red and coralline crags; also in the Campinian beds of Belgium.

Mactra striata of Mr. Smith (Wern. Trans., vol. viii. pl. 1. f. 22) appears to be a variety of this.

12. Mactra truncata, Montagu.

, fossil. In the Forth beds (of the Glacial epoch?).

, living. The British Seas.

13. Mactra subtruncata, Montagu.

, Mactra cuneata, Woodward.

, fossil. In the mammaliferous crag at Thorpe. In the Forth beds.

, living. In the British and Northern Seas.

Note. Appears in the red crag.