whettier they may be traced in formations syn-chronic with the glacial beds, is of no little interest and geological importance.
Whilst eocene, miocene, and older pliocene marine beds,—represented in our own country by the London clay, and the coralline and red crags,—are found in many parts of the north and middle of Europe and America, the "newer pliocene," such as is typified by the Sicilian tertiaries, those of Rhodes and other parts of the Mediterranean basin, is nowhere present within the area of the marine glacial beds, which, on the other hand, are nowhere to be met with within the area of the marine tertiaries of the Sicilian type. The latter, however (as we have already seen), includes a number of characteristic glacial forms which no longer exist in the same marine provinces, but are restricted to the northern or Celtic Seas. It is, therefore, extremely probable—I may say certain—that the glacial formations are "newer pliocene," and the SicUian tertiaries contemporaneous with the northern drift. As the sea in which those tertiaries were deposited communicated with the glacial seas, we might expect, à priori, to find among the relics of that ancient Mediterranean the still-surviving species which had lived in our seas previously to the glacial period, but had retired during its continuance.
The following table will shew that our search has not been in vain:—
Table of British existing Testacea which inhabited our area before the Glacial Epochs but during it had retired to other seas.
| Species. | Formations of Older Date than Northern Drift in which they occur in Britain. |
Foreign Newer Pliocene beds in which they occur. |
| Gastrochæna pholadia. | Coralline crag. | Sicily. |
| Thracia pubescens. | Coralline crag. | Sicily. |
| Lepton aquamosura? | Coralline crag. | |
| Pandora margaritacea. | Coralline crag. | |
| Montecuta 8ubstriata. | Coralline crag. | |
| Montecuta ovata. | Coralline crag. | |
| Kellia suborbicularis. | Coralline crag. | Sicily. |
| Lucina rotundata. | Coralline and red crags. | Sicily. |
| Tellina donacina. | Coralline crag. | S. Italy, Archipelago. |
| Psammobia vespartina. | Coralline crag. | Sicily, Archipelago. |
| Psammobia scopula. | Coralline crag. | Sicily. |
| Psammobia florida. | Coralline crag. | S. Italy. |
| Cytherea chione. | Coralline crag. | Sicily, Archipelago. |
| Venerupis irus. | Red crag. | Sicily, Archipelago. |
| Pullastra Virgines. | Red crag. | Sicily. |
| Venus ovata. | Coralline and red crags. | S. Italy, Archipelago. |
| Isocardia cor. | Coralline and red crags. | S. Italy, Archipelago. |
| Cardium nodosum. | Coralline and red crags. | |
| Arca noæ. | Coralline and red crags. | S. Italy, Archipelago. |
| Arca raridentata. | Coralline crag. | S. Italy. |
| Modiola discora. | Coralline crag. | Sicily. |
| Pinna ingens? | Coralline and red crags. | |
| Lima fragilis. | Coralline and red crags. | Sicily, Archipelago. |
| Lima subauriculata. | Coralline crag. | Sicily. |
| Pecten tumidus. | Coralline crag. | Sicily. |
