322
CEMENT STONE AT NACTON AND SEPTARIA GENERALLY
considerably harder than any calcareous cement stone yet formed in a similar way in Reading Beds. There cannot be many such examples of sheets of rock in the populär sense of the word at or near surface in Suffolk—excluding erratics. Miss Willis has kindly pointed out to me a short reference to septaria in our Proceedings for 1938, Vol. I, Pt. 1, xxx. F.
H. A.
ENGLEHEART.
NOTES ON CRAG PALAEONTOLOGY—1 By P.
G.
CAMBRIDGE
SYNOPSIS : The genera Ostrea, Cyprina and Teilina as understood by Searles V. Wood are reviewed and a species new to the Crag, Glibertia prosperi van Meulen, is recorded.
It is now over one hundred years since Searles V. Wood commenced his famous work on the Crag Mollusca and although considerable work has been done on the recent mollusca, involving many alterations to the older and better known names, no comprehensive work on the Plio-Pleistocene shells has been published in this country for many years. The author hopes to be able to review the Crag fauna in a series of articles of which this forms the first. The term Crag is used loosely in these notes for convenience, in place of the more accurate but clumsy term Plio-Pleistocene, to indicate the related Coralline (Gedgravian) and Red (Ipsvician) Crag. The Norwich Crag (Icenian) is recorded separately. As a matter of convenience the boundary between the Pliocene and the Pleistocene is placed by most modern writers at the base of the Waltonian. How long a period of time elapsed between the deposition of the Coralline Crag and the Waltonian Red Crag is not known, but certain Continental horizons are missing from the succession in this country. The occasional appearance of worn examples of Angulus benedeni (Nyst), Surculites intorta (Brocchi) etc., in the area of disturbed Crag between Felixstowe and Ipswich would seem to point to the destruction of some Crag beds and the incorporation of the remnants in the Newbournian Crag. T h e writer has been greatly assisted by Dr. L. R. Cox and Mr. Castell of the British Museum, L. v. d. Slik of Rotterdam, Dr. M. Glibert of Brüssels, and others who have helped with