OF NORFOLK AND SUFFOLK. 323 



myself have been engaged, of the land and freshwater shells 

 obtained from the superficial lacustrine or fluviatile deposits 

 of certain parts of Norfolk, Suffolk, and the basin of the 

 Thames, that the proportion of recent species in these forma- 

 tions is much greater than in the Norwich crag, exceeding 90 

 or 95 per cent., and which I therefore refer to the newer plei- 

 ocene or pleistocene period. ■ I allude, not only to certain 

 deposits at Cromer and Mundesley in Norfolk, the shells of 

 which have been collected by Mr. Fitch, of Norwich, but al- 

 so to those of Stutton, Grays, Ilford, and other places near 

 London; many of which have long been celebrated for the 

 remains of extinct Mammalia. 



The chronological order in which these various tertiary 

 groups follow each other in an ascending series, namely, 1st, 

 the coralline crag ; 2ndly, the red crag ; 3rdly, the mammal- 

 iferous or Norwich crag ; and 4thly, the lacustrine strata, with 

 mammalian remains ; — has been correctly indicated by Mr. 

 Charlesworth, in a paper communicated by him in 1836, to 

 the British Association. In that paper he stated that the pro- 

 portion of extinct to recent shells had not then been ascer- 

 tained. It is now satisfactory to find that the palaeontological 

 test of age, as derived from the relative approach to the recent 

 Fauna, is perfectly in accordance with the independent evi- 

 dence drawn from superposition, and the included fragments 

 of older beds. At the same time, the comparative proportion 

 of recent species in the several formations affords us, I con- 

 ceive, a considerable insight, not only into the order of se- 

 quence, but also into the relative distances of the times at 

 which the deposits were formed. 



Extension of the Norwich Crag into Yorkshire. — In a for- 

 mer number of this Magazine (vol. viii. o. s. p. 355), Mr. Wil- 

 liam Bean of Scarborough has described a deposit of sand 

 and clay, containing marine shells, as occurring near Brid- 

 lington quay. It was exposed, he says, for a few yards only, 

 on the north side of the harbour, at low water, near the plea- 

 sure-ground called the "Esplanade." He now informs me 

 (May, 1839), "that the spot is inaccessible, as the ground has 



1 In the Appendix to the French translation of my ' Elements of Geolo- 

 gy,' I have proposed, for the sake of brevity, to substitute the term Pleio- 

 cene for Older Pleiocene, and Pleistocene for Newer Pleiocene, from the Greek 

 nteiarov, most, and naivog, recent. I have been induced to make this inno- 

 vation, because in proportion as the progress of science calls for subdivisions 

 of these periods, the longer terms have become more inconvenient. We 

 have often for example, to speak of the older and newer portion both of the 

 older and newer pleiocene epochs. To the pleiocene period I have referred 

 those strata which contain between 40 and 70 per cent of recent species of 

 shells ; to the pleistocene those in which the per-centage exceeds 70. 



