Correspondence — A. Bell — S. V. Wood. 431 



deposited : First, the Lower Tertiaries, then Antwerp beds, then the 

 Forest-bed, then Freshwater, then Fluvio-marine beds (including 

 the Norwich Crag), then, in increasingly deeper water, the Chilles- 

 ford Sands and Clays (including the Aldeby or Taylor's Crag), then 

 the Marine pebbly-beds, and then the Lower Boulder-clay. 



This succession of strata is borne out by the Mammalian remains, 

 which are found in the Stone-bed upon the surface of the Chalk, 

 which consists of flints abraded from the Chalk. To such an extent has 

 it been abraded by pluvial action and strong currents, that the Chalk 

 at Hunstanton is reduced to nil ; and there can be no doubt it was 

 once deposited there, as in other parts of the county, from the immense 

 masses of Chalk-with-flints which are bouldered in that district. 



The Mammalian remains consist of the Mastodon Arvernensis, the 

 Elephas meridionalis, and a great variety of deer and other animals ! 

 The Mastodon is found in the Stone-bed associated with the Eleplias 

 meridionalis, but is not found in the Forest-bed. The Elephas 

 meridionalis abounds in the Forest-bed, but has not been discovered 

 in the Fresh-water, or Fluvio-marine beds, including the Norwich 

 Crag. The so-called " Mammaliferous Crag," when united with the 

 Stone-bed, was said to yield the Mastodon and Elephas meridionalis, 

 but is now proved to be almost non-mammaliferous. Mr. Grunn 

 also pointed out that the Bone-bed in Suifolk, upon the surface of 

 the London Clay, containing the debris of Miocene-beds, is formed 

 under similar conditions to the Stone-bed in Norfolk, and that the 

 changes of the fauna indicate the long periods of time occupied by 

 these several and respective formations. 



OOS/S-ESIPOilTIDIEJIsrOIB. 



TTI^IO LIMOSUS, NILSSON, IN THE CRAG. 

 Sir, — It is so seldom that the opportunity offers of adding to the 

 lists of fossils of the Post-glacial freshwater gravels, any species 

 foreign to the present British fauna, that the discovery of a fine 

 Unio may be regarded with some interest. The species referred to 

 is the Ifnio limosus of Nilsson, Hist. Moll. Succ, p. 100, and is 

 figured by Kossmasler, IconograpMe, fig. 199. It lives in the rivers 

 of Sweden, Denmark, and Northern Germany. My largest speci- 

 men measures 2|-in. lat. 1^ long. Locality, Barnwell, near Cam- 

 bridge. Mr. Jesson, I believe, was the discoverer of this interesting 

 addition to our fossil fluviatile fauna. Alfred Bell. 



PURPURA LAPILLUS IN THE COEALLINE CRAG. 



Sir, — "With reference to the article in your last Number, on a fossil 

 Hydractinia from the Coralline Crag, by Dr. Allman, enveloping two 

 specimens of Purpura lapillus, I woul.i remind your readers that this 

 Mollusc is at present unknown from the Cor. Crag. Has Dr. Allman 

 found it ? Searles V. Wood. 



Bkentwood, Essex. 



