GASTEROPODA. Ill 



the 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 bo seen in Valvata antiqaa, from the Fluviatile deposits of Grays 

 and Clacton, than can be pointed out among those of this genus which I have con- 

 sidered 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 dis- 

 tinct 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 striaa, and these same markings may be seen upon 

 specimens I have myself collected at Hordwell ; and the present shell I have pre- 

 sumed 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 Paludinas, 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 transporta- 

 tion, 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 impurum. Drop. Moll. p. 36, pi. 1, fig. 19, 1805. 



Bithinia tentaculata. Gray. Turt. Man. 2d edit. p. 93, pi. 10, fig. 120, 1840. 



— S. Wood. Catalogue 1842. 



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

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



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



P. Testa ovato-conoidcd, laevigata, politd, pcllucidd ; anfractibus quinque ; ultimo 

 tumido, ventricoso ; spird elevatd ; apice acuio ; aperturd ovatd, superne acuminata. 



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

 and ventricose ; spire elevated ; apex acute ; with an ovate aperture, slightly im- 

 pressed by the body whorl, and acuminated at the upper part. 



Axis, -| an inch. 



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



