GASTEROPODA PECTINIBRANCIIIATA. .)YJ 



The eyes of the snail are on the exterior oase of the tentacula ; the foot is small. There is a great number of 

 fossil species ; and we ought to unite with it the Prolo, Defr. 



The Sealaria baa the turreted spire of Turritella, with the aperture of Delphinula, but the spire is covered with 

 longitudinal, elevated, rather acute ribs, and the mouth is encircled with a varix. 'Die tentacula and penis of 

 the animal are long and slender. The principal species, the Turin) tealarit, Linn., or the Wentletrap, lias long 

 been famous for the high prices given for a specimen. It is distinguished by its whorls being separate from each 

 other. A small species without this peculiarity (Turbo c/at/irus, Linn.), is common in the Mediterranean. 



We may arrange here some terrestrial or lacustrine subgenera, whose shells have au entire roondiafa nperculated 

 aperture. Of this number are the Cyelostoma, Lam., distinguished from all others by being terrestrious ; and in 

 place of branchiae, there is a vascular network on the parietes of the pulmonic sac* In all other respects, Cyelo- 

 stoma resembles the animals of this family. The spiral shell is finely striated in the direction of its rounded 

 whorN. and, in the adult, the aperture is encircled with a small raised rim, and closed with a round thin opercu- 

 lum. The Turbo elegant, Linn., found in woods, under stones and moss, is the type of the genus. 



The Yalvata, Mull., live in freshwater. Their shell is obtusely conical, with a round operculated mouth ; and 

 the snail, which has two slender tentacula, and eyes at their inner base, breathes by means of branchiae. In our 

 native V. crislala, Mull., the branchia, in the shape of a miniature feather, protrudes from under the cloak, and 

 floats in the water with a vibratory motion, when the animal wishes to breathe. f On the right side there is a fila- 

 ment that resembles a third tentaculum. The foot is two-lobed in front. The penis of the male is slender, and 

 lies in the respiratory cavity The shell, scarcely three lines in height, is corneous, obtuse, and umbilicated. 



It is necessary to classify here some purely aquatic snails, which formerly made a part of the genus 

 Helix, since the shell had the crescent-like aperture that constituted the character of that genus. + The 

 three first genera are nearly allied to Turbo. Thus 



The Paludina, Lam. — 

 Have been separated from Cyelostoma because they have no rim or varix round the aperture ; because 

 this, as well as the operculum, has a little angle above ; and because the animal, having branchiae, must 

 live in water. It lias a very short proboscis, two setaceous tentacula, eyes seated on the external bases, 

 a small membranous fin on each side of the body in front, the anterior margin of the foot lobed, the 

 fin of the right side folded into a small canal to introduce the water into the respiratory cavity, an 

 approach to the siphon of the following family. In the common species (lldii ofoipara, Linn.), the 

 female is viviparous, and we find the young, in spring, in the oviduct, in all stages of develupenient. 

 Spallanzani assures us that the young, kept separate from the moment of their birth, can give birth to 

 others without having copulated, as happens with the Aphides. The males are, notwithstanding, as 

 common as the females, their organ issuing from a hole in the right tentaculum, which is thus made 

 larger than the other, and affords a character to know the sexes by. 



In the sea there are some shells that differ from Paludina only in their superior thickness. These arc 



The Littorina, Fcruss. 



The common species, or Periwinkle, swarms on our coasts, and is eaten. [The Lacuna of Turton is 

 a Littorina with a perforation in the pillar.] The Monodon, Lam., differs from Littorinaf in having a 

 blunt tooth at the base of the columella, which has in some also a fine incisure. Several are cre- 

 nuhited on the outer lip. The animal is more ornamented, carrying in general on each side three or 

 four filaments as long a^ the tentacula. The eyes are elevated on pedicles on the miter side of the root 

 of the tentacula. The operculum is round and horny. 



Trochut tettelattu, Linn., is an abundant example on the French coast. 



Thk I'm \»i \m ii \. Lam. — 

 Have a shell similar in shape to that of Limneus and Bulimus, but the aperture is cli sed who a calca- 

 reous operculum, and the base of the columella is sensibly Battened and without an umbilicus. The 



shells are much sought after by amateurs, from the beautiful speckled manner in which their various 



colours are disposed. Their snail has two long tentacula, with the eyes on tubercles at their exterior 



bases, double lips einaiginatcil and fringed, as well as the lateral tins carrying each three filaments. 

 [PL I un., is nearly allied to Phaaianella, from which, howei er, it may be distinguished by the prunes 



of the anterior part of the pillar. There are six species known, one of which is so common on the shores of the 

 Isle of France that the rocks, in some places, are covered with it.] 



r tt.U rem, in M.rfc Frni««»c, with Crclnuoma mid llelicini, 



.-. [which hee been 

 idople d by Rue, »iul ni.nv oil,. intwemnted 



•by the anatoi |irenbylhc Hit. Mr. Berkeley 



in the 



t llmcc Dr. Fleming wr»» Induced <<> institute the .irdrr ( 



la far Ibe genu, which he «/ierw«r.i- i Ih the H udl- 



i — Kit. 

 I I'll, y i. •intitule the f«mlN Klllp—tom I 



V.o. 



