GASTEROPODA. Ill 



same species. As a general character, the specimens from the Mammaliferous Crag 

 have the volutions rather less rounded or convex than those from Hordwell, although 

 there is considerable variation, in that respect, in the shells from both formations. 

 A much greater variation of form in the volution, as well as in size and elevation, may 

 be seen in Valvata antiqua, from the Fluviatile deposits of Grays and Clacton, than can 

 be pointed out among those of this genus which I have considered identical, and that 

 shell is now considered by most conchologists as only a variety of V. piscinalis. In 

 the specimens of this species from the Crag the apex is generally more or less eroded, 

 while it is rarely so in those I have procured at Hordwell, in which it is rather sharp 

 than otherwise. 



In examining some specimens from the Nile, in the British Museum, I could detect 

 no differences by which they could be fairly considered as specifically distinct from the 

 Hordwell species, and upon another tablet, in the same splendid collection, were 

 specimens bearing the locality of China, which even more resembled the Hordwell 

 shell; some of these have a subcarinated form of volution, with occasionally a few 

 obsolete spiral striae, and these same markings may be seen upon specimens I have 

 myself collected at Hordwell ; and the present shell I have presumed to be the prolonged 

 existence of the British Eocene species. The animals of this genus, in the recent state, are 

 now found inhabiting waters only that are quite fresh, while those from the Mammaliferous 

 Crag are mixed with marine shells in greater numbers than could be supposed to be 

 by an accidental introduction as dead specimens. The Paludinae, therefore, of this 

 period, must have either inhabited waters within the reach of the marine tide, or they 

 must have been carried by the streams in large numbers to where they are now found. 

 I am inclined to believe they lived very near to their present locality, as they bear no 

 marks of transportation, and young specimens are by no means scarce. 



Fig. 1 a is from the cabinet of Mr. Wigham. 



2. PALUDINA TENTACULATA. Linn. Tab. XII, fig. 2. 



HELIX TENTACULATA. Linn. Syst, Nat. p. 1249, 1766. 

 Mont. Test. Brit. p. 389, 1803. 



CYCLOSTOMA IMPUHUM. Drop. Moll. p. 36, pi. 1, fig. 19, 1805. 

 BITHINIA TENTACULATA. Gray. Turk Man. 2d edit. p. 93, pi. 10, fig. 120, 1840. 

 8. Wood. Catalogue 1842. 

 Morris. Cat. of Brit. Foss. p. 139, 1843. 



PALUDINA IMPUBA. Lam. Hist, des An. sans Vert. 2d edit. torn, viii, p. 514, 1835. 

 Rossmasler. Icon. vol. i, p. 107, t. 2, fig. 65, 1836. 



P. Testa ovato-conoided, leevigatd, politd, pellucidd ; anfractibus quinque ; ultimo tumido, 

 ventricoso ; spird elevatd ; apice acuto ; aperturd ovatd, superne acuminatd. 



Shell ovato-conoidal, smooth, and polished ; whorls five, convex, the last large and 

 ventricose ; spire elevated ; apex acute ; with an ovate aperture, slightly impressed by 

 the body whorl, and acuminated at the upper part. 



Axis, ^ an inch. 



Locality. Mam. Crag, Bulcham, Bramerton. Recent, Britain. 



