108 MOLLUSCA FROM THE CRAG. 



Paludestrina,* jyOrh. 1838. 



Saban.ea. Leach MS. 1818. 

 Hydrobia. Hartman, 1821. 

 LiTTORiNELLA. Brown, 18-13. 

 Paludinella. Pfeiffer, 184 — (?). 

 — Lovin, 1846. 



Gei). 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 corneous 

 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 laminae, 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 sdbumbilicatus. Mont. Test. Brit. p. 316, 1803. 



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

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



— Bujardin. 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 conicu, turritd, Itemgatd, subperforatd ; anfractibus quinque, convexis, tumidis ; 

 suturis profundis ; apice ohtustmculo ; aperturd ovatd, piP-ntremd integrd ; labro simplici, 

 labia subrejlexo, 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 peritremc; 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 inter- 

 mediate, between P. vlveB 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-cEshtarina, belonging to an estuary. 



