PISIDIUM HENSLOWANUM. 47 



BemarJiS. — Mr. B. B. Woodward informs me that Mr. Chatwin, late of the 

 Geological Department of the British Musenm (Natnral History), has drawn his 

 attention to an immature specimen in their collection which proves to l^e the right 

 valve of the present species. It was obtained from the Coralline Crag of Sutton 

 by R. Gr. Bell and bears a label to that effect in his writing, being the only fresh- 

 water shell known from that horizon; it has been found, hoAvever, in the Pleistocene 

 deposit at Edmonton by Mr. S. H. Warren. 



P. Hensloivanum was regarded by Jeffreys as a variety of P. fontinale, by other 

 authorities it is considered distinct. It seems to be specially characterised by the 

 lamelliform appendicula referred to above. 



As already stated, most of the non-marine mollusca described above have been 

 obtained from the Norwich, or, as I prefer to call it, the Icenian division of the 

 Crag. They are more common at certain localities in the neighbourhood of 

 Norwich than at others, as at Bramerton for example, probably representing spots 

 near which streams discharged into the Crag sea. The wide and apparently 

 continuous area covered by these deposits, extending in one direction from Norwich 

 to Aldeburgh in Suffolk and in another to Yarmouth and Lowestoft, suggest the 

 existence of a wide sandy bay, with shores gradually retreating to the north and 

 to the east, rather than that of an estuary. Non-marine mollusca occur also in 

 the Butleyan stage of the Red Crag at Hollesley and in one pit at Butley in the 

 special seam before referred to, as well as in that near Butley Abbey. 



The land and fresh-water fossils from the Butleyan and Icenian Crag are 

 generally those of living British shells having a wide geographical distribution. 

 A few have been met Avith, hoAvever, Avhicli Messrs. Kennard and B. B. Woodward, 

 unable to refer to any species known to them, have described as Limnsea hutlei/ensis, 

 L. Woodi and L. Harmeri. Corhictda fluminalis, moreover, is found generally, 

 though not abundantly, in the Icenian deposits, and very rarely in the later zones 

 of the Red Crag. The latter species occurs in the Pleistocene deposits both of 

 this country and the continent, though at present it is not known from any locality 

 nearer than the river Nile. 



The few non-marine forms Avliich have been collected from the earlier portions 

 of the Crag, the Gedgravian and the Waltonian, are Avith one exception of a 

 different character. From the Gedgravian Ave have Pi/ramidnla suttonensis, not 

 knoAvn living, of a Madeiran type, with another extinct shell, Glausilia pliocena. 

 From Walton-on-Naze, Pyramidula rysa allied to a Madeiran shell, Hygvomia 

 incarnafa non-British, Helicodonta lens inhabiting Morea and the Grecian Islands, 

 and Heliv lactea a southern species; from Oakley, Pomatias Harmeri an extinct 

 form. Such facts, as far as they go, siipport the vieAV of the separation of the 

 Waltonian fauna from that of the later horizons of the Crag. 



It may be interesting to notice that none of the non-marine Crag mollusca 



