110 MOLLUSCA FROM THE CRAG. 



Paludina,* Lamarck. 

 Helix (spec.) Linn. 



Gen. Char. Shell ovato-conical, or subglobulous, and in the recent state thin, 

 corneous, or semitransparent ; spire more or less elevated, with rounded or convex 

 volutions ; aperture subcircular or ovate, slightly impressed by the previous whorl, 

 and somewhat angulated at the upper part ; operculum corneous or calcareous, 

 formed of concentric laminse. 



Shells belonging to this genus in the recent state are found in water that is 

 quite fresh, and the habits of the animal are much like those of Lymnaege, although 

 it is said to be furnished with pectinated branchiae. 



This genus first appears in the Wealden formation in what is considered by 

 Dr. Mantell to be a fresh-water deposit, or probably the embouchure of an enor- 

 mous river. In the Eocene formations of this country at Hordwell, a species of 

 this genus is found associated with what may be considered as purely fresh- water 

 animals, while the species found in the Mammaliferous Crag are mixed with 

 decidedly marine species. 



1. Paludina lenta. Brander. Tab. XII, fig. 1, a — c. 

 Helix lenta. Brand. Foss. Hanton. fig. 60, 1766. 

 Vivipara lenta. J. Sow. Min. Conch, t. 31, fig. 3, 1813. 



— CONCINNA. - - - t. 31, fig. 4-5. 



Cyclostoma unicolor. Oliv. Voy.pl. 31, f. 9 a, b. 



Paludina lenta. Besh. Coq. foss. des Env. de Paris, p. 128, pi. 15, fig. 5-6, 1825. 



— SEMICARINATA. .... p. 127, pi. 15, fig. 1 1-1 2. 



— media. Woodward. Geol. of Norf. t. 3, fig. 5-6. 



— ROTUNDATA. - - - t. 3, fig. 7, 1833. 



— OBSOLETA. - - - - t. 3, fig. 4. 



— unicolor. Lam. Hist, des An. sans Vert. 2d edit. torn, viii, p. 513, 1838. 



— — S. Wood. Catalogue 1842. 



— — Cailliaud. Voy. a Meroe, pi. 60, fig. 7. 



— — Savigny. Egypt, pi. 2, fig. 30. 



B. Testa ovatd, conoided, crassd; apice acuto ; spird elevatd ; anfractibus quinque, 

 rotundatis, lavigatis ; aperturd obovatd, superne acuminata, peristomate integro ; umbilico 

 obtecto. 



Shell ovato-conical, with an elevated spire and acute apex ; volutions convex 

 and smooth, with occasionally a few obsolete strise ; aperture subcircular, slightly 

 acuminated at the upper part ; margin continuous, and umbilicus closed. 



Axis, 1 inch. 



Locality. Mam. Crag, Bramerton and Thorpe. Recent, Nile River. 



This shell is by no means rare at the above localities, and much too numerous 

 to be considered as casually introduced, like Planorbes, Lgmncea, and the Helices. 

 The specimens are variable in form, as may be seen in the figures referred to in our 

 own plate, and I have no doubt the shells figured by Woodward belong to one and 



* Palus-udis, a marsh or lake ; the general place of habitation for these animals. 



