LIMN.EA. ^ 101 



Genus III. LIMNiE'A *, {Lymnea) Bmguiere. 

 PL IV. f. 8, 9, 10. 



Body rather long and twisted in a spiral coil: 7?^a(i pro- 

 minent : tentacles short, triangular and flattened : foot oblong, 

 bilobed or notched in front and obtusely rounded behind, at- 

 tached to the upper part of the body as in Physa. 



Shell conic-oval or elongated : spii^e usually produced, 

 dextral or turning from the left to right. 



As in Physa, some of the species of Limncea, which 

 appear to form a transitional link between the two 

 genera, have their shells enveloped by an outer fold or 

 lobe of the mantle. These species have been generically 

 separated by some authors under the several names of 

 A^nphipeplea, Lutea, and Myxas. The difference be- 

 tween such and the typical species is, however, not greater 

 than between the two forms of Physa which I have above 

 noticed. All the species of Limnaa frequent shallow 

 and still waters ; and they are very prolific and grega- 

 rious. Their mode of propagation is very singular — three 

 or more individuals being united in a chain for that 

 purpose. Leach has remarked that, in consequence of 

 the sexual parts being distant fi'om each other, one in- 

 dividual is able, at the same time, to perform the function 

 of each sex with two others, as was first observed by 

 Geoffroy about the middle of the last century. The 

 spawn resembles that of the last genus. 



The generic name has been spelt by authors in no less 

 than nine different ways ; but the correct orthography is 

 undoubtedly LimrKsa (from Xifivalos:), as proposed by 

 Rang. 



* Inhabiting marshes. 



