Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/472

 Pholades, it would not be easy to fix upon a place in the Red Crag where the Testacea are on the spot where they lived*. We meet everywhere with finely comminuted shells and fragments of shells, with here and there a band of more perfect specimens, or a few such specimens dispersed amongst the comminuted fragments. Mr. Searles Wood, however, considers that at "Walton the conditions were such that many of the Crag Testacea lived on that spot. Notwithstanding the great number of shells occurring in the Red Crag, the abounding and characteristic shells consist of a few species only, and the larger proportion are more or less rare. Some species occur in countless numbers, such as Cardium edule, Pectunculus glycymeris, Tellina obliqua, T. crassa, T. proetenuis, Mytilus edulis, Pecten opercularis, Mactra solida, M. arcuata, Cyprina islandica, Lucina borealis, Purpura lapillus, Trophon antiquum, Nassa granulata, N. reticosa; while of many only a few specimens have been found, and of some only one or two specimens. In places, especially as we recede from the centre of the district, the beds become almost devoid of shells, or they occur only in patches. This may be partly owing to the original absence of shells, but it may also be due to the removal of the shells by percolation of rain-water through the beds ; for at places where the beds are consolidated by iron, casts of shells are occasionally met with, as in some pits between Woodbridge and Grundisburgh and elsewhere.

Mr. Searles Wood has given all the species he has procured from the rich localities of Sutton, Walton†, Bawdsey, Foxhall, and Newbourne. These localities are indicated by initials in the lists of Red- and Norwich-Crag fossils ; and therefore separate lists are not required. I have added some other localities.

Although some species are common throughout, there are many which have only a limited distribution, and which give to various localities their peculiar assemblages. This will be evident from the general list at the end, as well as from the following local lists of specimens, formed by me during occasional visits to the district.

From the pit the Butley Oyster Inn.

Astarte Basterotii.

— compressa.

— Omalii.

Cardita senilis.

Cardium angustatum.

— decorticatum.

— edule.

Corbula striata.

Cyprina islandica.

Diplodonta astartea.

Loripes divaricata.

Mactra ovalis.

Mya arenaria.

Mytilus edulis.

Nucula Cobboldiae.

— nucleus.

Pecten opercularis.

Saxicava arctica.

Solen siliqua.

Tellina crassa.

— lata.

— obliqua.

— praetenuis.

Dentalium costatum.

which he has found double. They are marked d in the general list.
 * Mr. A. Bell has obligingly given me a list of 54 species of Red-Crag shells

† See also Mr. Wood's separate list from Walton in Quart. Journ. Geol. Soc. vol. xxii. p. 542.