Page:VCH Suffolk 1.djvu/135

 MOLLUSCS in these Islands only from the estuary of the Thames, is of great interest, inasmuch as it adds another link to the chain of evidence that the Thames and the East Anglian rivers were formerly connected with each other and the Rhine in the broad valley now beneath the waters of the North Sea. Assemania has been found on the other side of this old valley in Belgium and Denmark. Paludestrina confusa on the other hand is known in the fossil state at West Wittering and Stone on the Sussex and Hants seaboards. 'Jaminta tripltcata, another recent discovery, though considered by some competent malacologists to be merely a variety of y. muscorum^ is retained as a valid species. The pretty little molluscs referred to the genus Vertigo seem very partial to Suffolk, all the British species save V. alpestris, which is a northern form, being represented. Of these the latest addition has been V. Moultnsiana, and though its claim to be considered a Suffolk shell at present rests on the presence of a single, recently dead, shell, there can be no doubt of its existence in some one of those swamps in which it loves to dwell and into which the ordinary collector does not love to penetrate. The species is now known in nine English counties from Derby to Devon, as well as in Galway, and occurs besides in several post-tertiary deposits, so that it is widely spread but probably largely overlooked on account of its uninviting habitat. The Roman snail {Helix pomatid) here attains the furthest north- easterly limit of its distribution in England. Originally thought to have been introduced by the Romans, whence its popular name, it has now been proved an old inhabitant by its occurrence in a deposit of pre-Roman age near Reigate. In a Pleistocene deposit at Stutton the following species that no longer live in the British Islands have been found : — Eulota fruticum, Paludestrina marginata, Um'o /ittora/is, Corbicula Jiuminalis, and Pisidium astartoides. The first three still live on the Continent ; Corbicula dwells to-day in the Nile; while the last seems entirely extinct. A Holocene deposit at Knettishall has yielded a continental form, Planorbis vorticulus, no longer living in Britain. The literature dealing with the mollusca of Suffolk is not extensive. The most important papers are : — One by the Rev. Carleton Greene {Proc. of the Suff. Inst, of Arch, and Nat. Hist., vii, 275; Additions, xi, 424), and two, one on East, one on West Suffolk, by Mr. A. Mayfield {Journ. of Conchology, x, 295 ; xi, 333). From these, with the assistance of stray notes and the Records of the Conchological Society, the appended list has been compiled. 97 13