52 EAMBLES IN SEARCH OF SHELLS. 



for fish-ponds no doubt suggested the specific name 

 piscinalis. 



Another little water snail is Bythinia tentaculata, 

 which in appearance (PI. VI., fig. 10) is not unlike 

 a miniature PahicUna, already described; but in the 

 former genus the animal is oviparous instead of 

 ovoviviparous, and sessile-eyed instead of stalk-eyed. 

 Mr. Gwyn Jefireys has pointed out that, although the 

 derivation 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, especially in the marshes below London, 

 where they lay their eggs in three long rows on 

 stones, as well as on the stalks and leaves of water 

 plants. The animal floats or creeps on the under 

 surface of the water, and is said to be carnivorous as 

 well as herbivorous. It has been found commonly 

 in ditches at Fulham. A second species of the 

 genus, named Leachii, after the late Dr. Leach, has 

 been found in the Woolwich Marshes, but it is much 

 more local than the last named, and less abundant. 

 In company with the two last named may be found 

 Hydrohia similis and Assiminia gray ana, but these 



