218 LIMNiEADiE. 



their spawn on stones In small gelatinous globules, 

 each containing many small eggs. {Pfeiffer, t. 161. 

 f. 21.) They have a retractile (and not exserted, as 

 described by Guilding) male organ at the base of the 

 left tentacle. 



These animals sometimes swim about on the sur- 

 face of the water, like Limncei, with the back down- 

 wards. In fact they are Limnai, with very short 

 conical, instead of long spiral bodies. 



Mr. Jeffreys doubts their being Pneumonobran- 

 chous ; and Dr. Fleming in one of his works refers 

 them to the genus Crepidula ! and in his British 

 Animals to the Pulmonifera. The tongue is a broad 

 spiral band twisted at the end, longitudinally keeled, 

 and set Avith numerous close cross-bands of minute, 

 close-set, equal, short triangular spines directed 

 backwards and furnished with a simple membrana- 

 ceous margin on each side, half as broad as the tongue 

 Itself; the stomach very much resembles the gizzard 

 of a fowl, has a strong muscular band on each side, 

 and is nearly filled with small flinty particles. 



The Ancyli prefer clear water, living attached 

 to stones and the sunken stems of aquatic plants. 

 They often ascend and attach themselves to damp 

 rocks of waterfalls. 



During the summer, when the waters are low, they 

 secrete themselves in the mud and await the return of 

 the water. The shell completely covers the animal ; 

 and when they walk, the end of the tentacles, and 

 rarely the tip of the muzzle, appear beyond the edge 

 of the shell. They feed principally on the radical 

 fibres of water plants, small confervas, and green 



