28 PALUDINID&. 



are oviparous, instead of ovoviviparous ; their eyes are 

 not placed on pedicles, or foot-stalks, but are sessile ; 

 the operculum is testaceous, instead of horny, and 

 its nucleus is nearly central ; the right tentacle of 

 the male is of the same size as the left. Gwyn 

 Jeffreys very justly remarks that "although the de- 

 rivation of the word Bythinia would imply that these 

 molluscs inhabit deeper water than others of the 

 same family, such is not the case ; they generally 

 frequent small streams, canals, shallow ponds, and 

 ditches." B.C., vol. i. p. 59. 



They breed from May till August, and the eggs, 

 which vary in number from ten to seventy, are de- 

 posited on stones or aquatic plants, in three, or more 

 rarely in two rows, which form a transparent band. 

 The fry are excluded at the end of from twenty to 

 twenty-five days, and attain their full growth in about 

 two years. 



i. BYTHINIA TENTACULA'TA,* LINN. PL. IV. 



Body black or dark brown above, dirty grey beneath ; head 

 small, semi-oval ; tentacles filiform, considerably diverging ; eyes 

 prominent, somewhat oval, black ; mouth with a reddish margin ; 

 foot much broader than the snout, rounded in front, nearly 

 opaque, edges greyish ; tail bluntly rounded at its extremity, 

 half hidden by the operculum. 



Shell conical, moderately solid, rather glossy, semitransparent, 

 yellowish or brownish horn-colour ; closely and finely striate in 

 the line of growth and microscopically so in a spiral direction ; 

 epidermis thin ; whorls 5-6, convex, body whorl occupying 

 rather more than one-half of the length of the shell, apex some- 

 what sharply pointed ; suture oblique, rather deep ; moiith oval, 

 angulated above ; outer lip thick, and frequently furnished in- 



* Provided with tentacles. 



