320 APPENDIX. 



they were first placed, in having an obtuse instead of an acute apex, like all the species in that genus that I 

 have examined, and the texture of the shell is vitreous and clear, and when living was probably quite 

 transparent. The form much resembles that of Natica, but the peristome is continuous, and not impressed 

 by the body whorl, nor is the inner lip spread out as in the species of that genus. I know of nothing 

 strictly resembling it, and if the determination of the genus depend, as it is said, entirely upon the form of 

 the operculum, it will probably be long ere it is correctly determined by that character. 



PALUDINA PABILIS, S. Wood. 



PALUDINA LENTA. S. Wood. Crag. Moll., vol. i, p. 110. 



Since the publication of my first volume, wherein I had assigned the Crag shell as an identity with the 

 fossil from the Older Tertiaries, and considered them both as the progenitors of a shell now living in the 

 Nile, I have given to them a more extended examination, with an increased number of specimens, and have 

 reason to believe they are all three distinct. 



1 therefore propose the above name for the British Upper Tertiary Fossil, in lieu of the one it has 

 hitherto borne. 



PALUDINA MARGIN ATA, Michaud. Tab. XXXI, fig. 18, c, b. 



PALUDINA MAKGINATA. Mich. Comple. de 1'Hist. Nat. des Coq. Terr, et Fluv. de la France, 



p. 98, No. 11, t. 15, figs. 58, 59, 1831. 

 Lyell. Man. Elem. Geol., p. 127, fig. 112, 1851. 

 MINUTA. Strickland. Silur. Syst., p. 555. 



Lyell. On the Boulder Formations and F. W. Deposits of Eastn. Norf., 

 Phil. Mag., ser. 3, vol. xvi, No. 104, p. 354, fig. 4, 1840. 



Spec. Char. " Testa minima, pellucidd ovata, nitidd, albidd, longitudinaliter substriatd ; anfractibus 

 quinis, rotundatis ; aperturd ovato-rotundatd ; labro extus marginato ; apice obtuso, papillato. Operculum 

 ignotum." Michaud. 



Shell small, pellucid, ovate, naked, white, slightly striated longitudinally ; volutions five, rounded ; 

 aperture roundedly ovate ; outer lip outwardly marginated ; spire obtuse, papillated. Operculum unknown. 



"Dimensions, f and line." 



Recent, Draguignan, South of France, Carouge, near Geneva (Jeffreys). 



This species is, I believe, abundant at each of the localities in which it is found, and particularly so at 

 Clacton. The generality of specimens do not exceed the dimensions given by Michaud to the recent shell, 

 though some few of my fossils have attained to the tenth of an inch in length, from the elongation of the 

 spire, without increasing the number of volutions, in which case the suture is much deepened. The apex is 

 very obtuse, the vertex being flattened, with the apical or embryonic portion broad and inflated. The 

 outside of the aperture is strengthened by a thickened whitish rib, generally at a short distance from the 

 margin, which is sharp and plain ; the aperture is ovate, with the major axis in a longitudinal direction, 

 scarcely at all impressed by the body whorl. 



This is not now found living in Britain, and I have been unable to obtain any information respecting 

 the soft parts of the animal. The thickened margin would rather indicate its having a calcareous operculum, 

 like the genus Bithinia, but I have never found one, although the shell is very abundant. 



