• 40 



These animals are oviparous, a number being de^ ^ 

 posited in an oblong group on aquatic plants. 



BiTHiNiA TENTACULATA (The Tentacled Bithinia). 

 Figures 16 and 17. 



\1. I6.W 



The Tentacled Bithinia has been known for so many 

 years, that it would be difficult to say by whom it was 

 first discovered. 



It is a rather slender, semi-transparent shell, being 

 very smooth. The general colour is that of a yellowish- 

 horn, not unfrequently it is entirely incrusted with a 

 hrownish-hlack coat. There are five convolutions, the 

 lowest one being nearly as large as the whole of the 

 other four convolutions together. It is somewhat ven- 

 tricose, but varies ; occasionally shells are found much 

 more produced, without any increase in their ventri- 

 cosity. It also varies much iu the size it attains, in 

 some localities being almost twice as large as in others. 

 It has been noticed that where it attains the greatest 

 dimensions it is the least abundant. Bithiaia tentacu- 

 lata is without an umbilicus. The last, or uppermost 

 whorl, ends in a point. 



M. Bouchard Chantereaux informs us that the 

 Bithinia tentaculata lays its eggs from the month of 

 May to that of August. It usually deposits from thirty 

 to seventy in number at one time, which are yellowish 

 hyaline eggs, and are united together in a band, being 

 fastened firmly to aquatic plants or stones. The young 

 ones are hatched in from twenty to twenty-five days 



