BITHINIA. 



141 



which it seizes and guides into the Httle canal to fix it in its 

 destined locaHty. Then the animal cleans the body to which 

 it adheres anew, and deposits a second egg, repeating the 

 operation till all the eggs are expelled, and arranged in ri- 

 band-fashion, each band, when laid by an adtdt, consisting 

 of three rows. The whole process proceeds slowly, time 

 being left between each effort sufficient for the agglutination 

 of the egg. The young ones emerge at the end of from 

 twenty to twenty-five days, and do not attain full growth 

 until the end of their second year/' 



The shells of Bithinue are smaller and more hyahne than 

 those of Paludhm. The animal is purplish-black, speckled 

 with bright yellow, with long tentacles, thickened at the base 

 by the eye-swelling; a rather long, rounded proboscis; and 

 the foot somewhat bell-shaped. Of 



B. tentaculata, the shell is thin, smooth, horny, oval, with- 

 out any hollow behind the mouth ; 

 B. Leachii, the shell has the wliorls more rounded and se- 

 parate, and a hollow behind the mouth. 

 The BlfMnice frequent ditches, canals, and slow rivers in 

 almost every part of England. 



III. Valvata piscinalis is a little fresh-water mollusc, 

 which has the foot divided in front into two lobes. The 



