iQiQ. Stelfox. — Lake-Forms of Limnaea pereger. Ii 



quoting Dr. Ball's diagnosis of the sub-genus Cyclolimnaea, 

 of which L. involuta is the type species, states : " The 

 mantle covers a portion of the shell as in Amphipeplea." 

 I have been at some pains to trace the origin of this curious 

 myth, and find that the late Dr. Edward Perceval Wright 

 of Trinity College, Dublin, assured Jeffreys that the mantle 

 enveloped the shell. -^ Jeffreys at the same time was careful 

 to point out that neither Thompson nor Goodsir, in their 

 original accounts of the shell and its inhabitant, referred 

 to this peculiarity. Subsequent to the publication of "British 

 Conch ology,*' tiie statement has been frequently copied. 

 Whether Dr. Wright was the originator of it or not will 

 probably never be known now. Suffice it to say that there 

 is no word of truth in it ; nor is there any, I think, in the 

 suggestion that L. involiUa and L. praetenuis are in any way 

 closely related to L. glabra. 



Conchologists like myself, who in future may desire to 

 unite involuta and praetenuis with L. pereger, will no doubt 

 be in a quandary as to the correct name to apply to these 

 varieties as a whole. To employ the name involuta, which 

 possibly has priority, to cover all these fragile lake forms, 

 some of which have elevated spires and few of which possess 

 really intorted spires, seems absurd. Would it not be 

 desirable to restrict the appellation involuta to the form 

 found in Lough Crincaum and that of praetenuis to the shell 

 found in Lough Nagarriva ? Would not likewise the most 

 suitable name for the whole group be " var. lacustris," of 

 Leach, who in his Synopsis described as a species^Gulnaria 

 lacustris — a form of Limnaea found in the lakes of West- 

 moreland and Cumberland. His diagnosis is fairly in- 

 definite and could be used to cover all these lacustrine 

 forms, since the character Leach lays most stress on is the 

 " regularity of the grooves " which " at once distinguish 

 this from any other species." Mr. Huggins makes one further 

 important suggestion, namely, that this group of lake 

 Limnaeae may constitute a species distinct from the shells 

 found in rivers, canals and ditches, which we know also at 

 present as L. pereger. On this question I have kept an open 

 mind so far, but I am inclined to think that all connecting 



*■ See " British Conciiology, " vol. i., p. 104. 



