m 



to the oliscrvatioiii of MM. Quoy and Gaymard, a large pouch tillcil \\ith 

 air, and wliich may pobsilily l»e a swimming bladder. 



Tlie Laiii.slc-s, Muiitr., !iv<' Ai]Ji"i!Jllari;i^ with a wide s[iir-i! umbilicus. — The Ui-li- 



cilia. Lam., ffom the sliell, would seiTii to be Ampullarioi witli the rim ofthe aper- 



tuTL- reflected, AYhen thi.s rim is sliarp, the shells are AmjjulluiCi-, lilaiiiv., ;irid 



wlicn it is lilunt, the Oli/g/ric of Say. There is one species {Helicina iimh'ila, 



Lam.) remarkahkMor a white shelly ed3;e on the inner side of the operruknu. It 



■■~ — ^ appears tiiat the ori^^nnv of fes[)ir;ition are similar to Cyclostduia, and that the 



iL'. / .— . mpu ,in,i ruL,n..s,.. animals can live in thr (ij.cii air. [ The Helicins are land sljeils. .Mr. (iray lias 



p: ^ en amoiiograph of the g'enus in the 1st vol. of Ihe Ztiohujiral Journal ; but since its pnblication, the number of 



species has been donbled.] 



The ]\Ii:lani,e — 



Have a thicker shell, with the aperture deeper tliau wide, which expatidb at the part opposite the spire. 

 The columella has neither fold nor umliilicus. The spire varies greatly in its length. They live in 

 ri\ers,but there is no species in France. The animal has long tentacula, and the eyes are placed about 

 a third ^vay up on their outer side. 



The Rissof!, Freminv. {Acmea, Hartm.) differs from IMelania in having the rim of the aperture united all round. 

 [" All we have met with are littoral shells, and several species abound on our shores." — Soiverlnj. — MelnnopsiSy 

 Ferussae, witli ncaii)- the same form as Welania, has a callosity at the columella, and a vestifje of an emargfination 

 near tlie base of the aperture, indicating a relatioushi]) wilh Terebra. The P/rt.'j;'?, Lam., have not merely this 

 sinus, but another on tlie opposite side. Like the .Mrhmia, tlie two Uist subgenera live in the rivers ofthe south 

 of Europe, ami nf \varm countries, [" and yet most nf the Pissil s|)eeies are found in beds that are considered by 

 geologists, ill tliis cuuntry, to be of marine formatinn."— -S'l^/zTrA//.] 



M'e incline to refer to this place in the system two genera separated from the Volutes, and which 

 luivc a considerable similarity to Auricula, )iut arc opcrculated, and have only two tentacula. Fii'^t, 

 Acteoiij Montf., (Tornaiella, Lam.), "with a convolute shell ; and, secondly, Pi/rcnnidclla, Lam., with a 

 turreted shell, whose columella is obliquely twisted and plaited. 



The Jaxthina*, Lam. — 

 Is widely separated from all that precede by the form of the animal. The shell has some resemblance 

 to our land snails, but the aperture is angular at its lower jiart and at its outer side, where, however, 

 the angle formed by the union ofthe upper ami Inwer haU!':^ t-t the outer lip, is niiicli rounded in most 

 of the species, and somewhat so in the comnnin nnc : the cnlumella straight and rhmgatcd, the inner 

 lip turned back over it. The animal ba> no npiTciilimi, but carries under its foot a ve.^il■^lar organ, 

 like a congt.'rics of j'oam-hubblcs, of solid cnusistciir) , that prevents creeping, hut servos as a bitny to 

 support it at the surface of the waler. The head is a cxlindi ical prnboscis ; and is tri-uiinateil witli a 

 mouth cleft verlicallv, and armed wiih liUle curved spines: im each snic uf it is a foi-ked Uiitaciilum. 

 The shells are of a violet colour ; and when the animal is irritated it jiours forth an cNorelion of dee[ier 

 blue to tinge the sea around it. 



Til'.' L//ii>pa, Itang, is a small conoid shell witlmiit an n]i.Tcidum, the body-whnrl lan^ei" than the siiire, and the 

 aiiertniT eiitin". The ardnnd li\es <in thr i:iilf-\\<i>il, whrnif it can su=]htii.1 itseltby a thread like a spider from 

 a ceiliiii;; and by the sann:- tliruad it can remnmit at pli>aMMr to the surface of the weed.] 



Thii; Nerita, Linn. — 

 Are shells with the columella in a straight line, which romh.-rs their aperture senjicircular or scmielliiitical. 

 It is generally large in proportion to the slicll, but al\\a\s closed perfectly with an operculum. The 

 spire is almost obsolete, and the shell semi-glubular-t 

 Natlae, Lam., are Nerit;i' w ith a 



the eyes sessile at their lia.-.es, and a honiv [or siielUJ (tpi'n-uhiin. [In Xcn/ojisi.^, ii^oweiby, their i 

 or sums in tlu' columella, which distinguishes it from Natica and Nerita, whose forms it seenis to em 



■ula, 

 ntch 

 rlf.] 



■ M. lit Bliii 



I'illi: 



tlii. 



M f-imily O^i/ftoin 



rnK-ncnu, 



rit<t, LSnii., constitute the ffimily Jlemicyrlustum 



