GASTEROPODA. 71 



Hydrobia ulv^e, Pennant. Supplement, Tab. IV, fig. 23. Crag Moll., vol. i, p. 109 



(as Pahidestrina ulvcs). 



Turbo vlvje, Penn. Brit. Zool., 4th ed., vol. iv, p. 132, pi. lxxxvi, fig. 120. 



Localities. Red Crag, Walton (Bell) ? Fluvio-marine Crag, Yarn Hill, near 

 Southwokl. Chillesforc! bed, Aldeby. Post-glacial, Gedgrave. 



This species I have not seen as fossil from either of those purely marine formations, 

 the Coralline and Red Crags. The specimen figured is from a formation at Gedgrave, 

 mentioned in vol. i, p. 109, which is, I believe, a post-glacial bed, where land and 

 freshwater shells of an old post-glacial period are intermixed with a re-deposit of Coralline 

 Crag derivatives. It has been found by Mr. Reeve in the Fluvio-marine Crag at 

 Bramerton, and by Messrs. Dowson and Crowfoot at Yarn Hill and Aldeby. This 

 species is given by Mr. Bell from Walton ('Ann. and Mag. Nat. Hist.,' Sept., 1870), 

 but I have not seen the shell. 



Hydrobia subumbilicata, Mont. Crag Moll., vol. i, p. 108, Tab. XI, fig. 2 (as 



Paludestrina subumbilicata) . 



Localities. Fluvio-marine Crag, Bramerton. Chillesford bed, Bramerton. 



This species, so very common in the Fluvio-marine Crag at Bramerton, is, I am 

 informed, very rare in the Marine Chillesford bed at that place, and I have not met 

 with it in the Chillesford bed elsewhere, nor in the Lower or Middle Glacial Sands. I 

 agree in the distinction drawn by Montagu between this shell and its congeners ulva and 

 ventrosa ; and distinct from all these is, in my opinion, Hydrobia t/termalis {Helix 

 octona?, Linn.), Crag Moll., vol. ii, p. 319, Tab. XXXI, fig. 12, to which I have referred 

 the shells found in the freshwater (older post-glacial) deposits of Clacton and Grays. 



Rissoa proxima, Alder. Supplement, Tab. IV, fig. 17. 



Rissoa pkoxima, Alder MS. Thompson, An. Nat, Hist., vol. xx, p. 174. 



Locality. Coralline Crag, Sutton. 



In deference to the British conchologists, I have separated two specimens which I had 

 considered as varieties of R. vitrea. They were pointed out to me by Mr. Jeffreys as 

 specifically distinct. The stria? with which they are covered (which are not very visible 

 in my fossils) appear to be the only character by which they can be distinguished. 



