200 
LIMNiEAD^. 
Fig. 48 . 
Limnceus pereger. 
The apex of the shell is often eroded or truncated 
(fig. 49); that is to say, as the upper part of the body 
is withdrawn from the tip, and the body moves 
forwards into the larger part of the shell, it forms 
a septum behind, and the part that 
is thus separated eventually falls off. 
Mr. Jeffreys, not being conversant 
with the physiology of the Mollusca, 
gives a curious explanation of this 
L. palustris. ^ i • i • 
phenomenon, which is not uncommon 
in the terrestrial and marine, as well as fresh-water 
Mollusca, In the absence of other nourishment, 
they (the Limncei) will even devour each other, 
piercing the shell near its apex, and eating away 
the upper folds of the inhabitants. This accounts 
(he proceeds) for the mutilated and often imperfectly 
repaired state of the upper volutions of some speci- 
mens.” {Linn. Trans, xvi. 371. But see Turton^^ 
Man. ed. 1. 78.; Gray^ Phil. Trans. 1833.) 
* Dr. Turton, by mistake, appears to think that the shells 
have “ a vascular connection ” with the animal. This is not 
Fig, 49. 
