218 
LIMNiEAD^. 
their spawn on stones in small gelatinous globules, 
each containing many small eggs. 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 Limnm^ with the back down- 
wards. In fact they are Limnm^ 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 with 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 
