MOLLUSCA FROM THE CRAG. 



me for the purpose of being figured, are sufficiently characteristic to be fairly identified 

 with one of the recent British forms ; and I feel justified in assigning it to L. peregra. 

 This is also found at Stutton and Clacton, but I have only met there with the more 

 ovate and less elongated variety. 



3. LIMN^A TRUNCATULA (?) Mull. Tab. I, fig. 8, a b. 

 BUCCINUM TRUNCATULUM. Mull. Verm. p. 130, No. 325, 1774. 

 HELIX FOSSARIA. Mont. Test. Brit. p. 372, t. 16, fig. 9, 1803. 

 LYMXEUS MINUTUS. Drop. Moll. pi. 3, fig. 5-7, 1805. 



FOSSARIUS. Turt. Man. fig. 108. 

 LIMNEA FOSSAUIA. Flem. Brit. An. p. 274, 1828. 

 LIMXEUB MINUTUS. Rossm. Icon. p. 100, t. 2, fig. 57, 1835. 



L. Testa pnsittd, ovato-conicd, perforatd, tenui,frayili ; anfractibvs quinque conveosis ; 

 suturis profundis ; spird elevatd ; apice acuto ; aperturd ovatd. 



Shell small, ovato-conical, perforated, thin, and fragile, with about five convex 

 volutions, and a deep suture ; spire elevated ; apex acute ; aperture ovate ; and a 

 slightly reflected pillar lip. 



Axis, \ of an inch. 



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



One small specimen, represented at fig. 8 b, sent to me by Mr. Wigham for the 

 purpose of description, appears to belong to this species ; it has the convex volutions, 

 deep suture, and open umbilicus, corresponding with those of the recent shell. Fig. 8 a 

 is the representation of a specimen from the cabinet of Mr. Lyell of a more doubtful 

 character ;* although more elongated than the general form of the recent species, it 

 appears to correspond in other respects, and I feel disposed to assign it to 

 L. truncatulus. This species is found in the truly Lacustrine beds of Stutton and 

 Clacton, corresponding precisely with the recent form. 



PLANORBIS/I* Mutter, 1781. 



Gen*. Char. Shell orbiculato-depressed, discoidal ; volutions apparent above and 

 below, convoluted upon a nearly horizontal axis, thin, light, smooth, and somewhat 

 corneous ; aperture simple, lunate, crescent-shaped, or subquadrate ; outer lip thin, 

 sharp ; inner lip slightly spreading over the body whorl. No operculum. 



The animals belonging to this genus are inhabitants of pure fresh water ; their 

 most favoured places of abode being in waters that are stagnant, although a few are 

 found in gentle streams ; but none are as yet known in those places to which salt 

 or brackish water has access ; the specimens, therefore, found in the Crag must of 

 course have been accidentally introduced, and are few in number. Shells of this 

 genus are formed upon a nearly horizontal plane, and some considerable disagreement 



* Mr. Lyell's specimen measures f of an inch, 

 t Etym. Planus, fiat, and orbis, a circle. 



