LIMNEA. 6 



The principal part of their food is contained 

 in the shmy matter which covers sticks and 

 stones beneath the water, and in the mud, 

 which is constantly found in the intestines. 



Doctor Gould informs me that towards the 

 end of the warm season, he has seen the 

 Limnese eating each other's shells, and as Mr. 

 Jeffreys has given the same account,* it is 

 most probably correct; although Mr. Gray 

 appears to doubt the fact, because the apex is 

 sometimes deciduous, from a different cause.t 



The genus Amphipeplea of Nilsson, unites 

 Limnea and Physa by characters common to 

 both, so that its situation is difficult to deter- 

 mine. It has the following characters in com- 

 mon with 



Limnea. Physa. 



Shell dextral. Shell short. 



Tentacles triangular. A lobed mantle. 



If the foot is short and oval, I would place it 

 under Limnea; if slender, and extended pos- 

 teriorly, it belongs to Physa, where I place it 



* Gray's ed. of Turton's Manual, p. 231. London, 1840. 



f To avoid unnecessary repetition under each genus, an expla- 

 nation of this circumstance, as well as of others appertaining 

 equally to all the genera, will be found in the Introduction. 



