108 MOLLUSCA FROM THE CRAG. 



Paludestrina,* D' Orb. 1838. 



SabanjEa. Leach, MS. 1818. 

 Hydrobia. Hartman, 1821. 

 Littorinella. Brown, 1843. 

 Paludinella. Pfeiffer, 184— (?) 

 — Loven, 1846. 



Gen. Char. Shell generally small, of an ovate or ovato-conical form ; spire more 

 or less elevated ; volutions convex and smooth, and in the recent state, of a cor- 

 neous or semitransparent texture ; aperture ovate ; operculum corneous and 

 spiral. 



Most of the known recent species of this genus are estuary animals, and some 

 are found where the water is occasionally fresh. They were separated from 

 Paludina by M. d'Orbigny in consequence of a difference in the structure of the 

 animal, which in this genus has the eyes at the anterior part of the base of the 

 tentacula, whereas in Paludina the eyes are at the extremities of the tentacles. In 

 the former the operculum is increased by spiral laminse, but in the latter (Paludina) 

 they are concentric. This genus nearly resembles that of Rissoa, the animals of 

 which are, however, more strictly marine. 



1. Paludestrina subumbilicata. Mont. Tab. XI, fig. 2, a — b. 



Turbo subumbilicatus. Mont. Test. Brit. p. 316, 1803. 



— thermalis (?). Linn. Syst. Nat. p. 1237. 

 Paludina muriatica (?). Lam. Hist, des An. sans Vert. 2d edit. torn, viii, p. 463, 1838. 



— Dujard. Mem. Soc. Geol. de France, torn, ii, pt. 2, 1837. 



Turbo minuta. Woodward. Geol. of Norf. t. 3, fig. 20, 1833. 

 Rissoa subumbilicata. S. Wood. Catalogue 1842. 



— Morris. Catal. of Brit. Fossils, p. 161, 1843. 



P. Testa conicd, turritd, laevigata, subperforatd ; anfractibus quinque, convexis, tumidis ; 

 suturisprqfundis; apice obtusiusculo ; aperturd ovatd, peritremd Integra ; labro simplici. 

 labio subreflexo, umbilico parvo. 



Shell conical, elevated, smooth, and naked, with five convex and rather tumid 

 volutions ; suture deep and well defined ; apex slightly obtuse ; aperture ovate, 

 with a continuous peritreme ; inner lip a little reflected over a small umbilicus. 



Axis, \ of an inch; diameter, \ the length of axis. 



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



This is an exceedingly abundant species in the estuary deposit at Bramerton, 

 and I have one doubtful specimen from the Coralline Crag. This shell appears 

 intermediate, between P. ulva and P. ventrosa, differing from the former in being 

 more elongated, and in having the volutions more convex, and from the latter in 

 having the same characters less prominent. 



* Etym. Paludina-cestuarina, belonging to an estuary. 



