t3oycott : Manganese in Land and Fresh-water Mollusca. 137 



{b). — Hyalinia is similarly generally high and sometimes 

 very high, but also sometimes quite low. 



Helix aspersa 



H. pomatia 



H . nemoralis 



H . hortensis 



Bulimir.us montanus 



B. o'rscurns 



Clausula laniinata 



CI. biplicata 



Siiccinea putris 



S. ele^aiis 



Ancylus fluviatilis 



A . lacustris 



Limnaea auricularia 



L. peregya 



L. stagnalis 



L. palustns 



L. glabra 



Planorbis corneus 



PI. complanatus 



Physa fon tinalis 



P. hvpnorum 



P. heterostropha ... 



Bitfiinia tentaculaia 



Paludina contecta. 



P. vivipara ...' 



Cyclostoma elegans 



Neritina fluviatilis 



Dreisssna polymorph a ... 



Unio pictorum 



U. tmnidiis 



Margaritana margaritifera 



Anodonta cygnea... 



A. anatina 



Pseudanodonta ' rothomagensis ' 



Sphaevium rivicola 



S. cnrneuni 



S. lacustre 



S. pallidum (ovale) 



Pisidiuni amnicum 



.0 a 



i s 



3 o 



17 

 16 



3 

 4 

 I 

 I 

 29 



55 



30 



6 



2 

 3 

 3 



0-6 



I 



0-4 



0-3 



19 

 46 

 38 

 24 



nil 

 nil 



3 

 103 



85 



19 



46 



3 



I 

 I 



7 

 6 



36 

 165 

 212 



113 



46 



73 

 0-3 



0-2 



0-8 



78 



6r 

 8 

 5 

 4 

 3 

 9 



16 



4 



6 



3 



6 

 trace 



I 

 07 



0-5 

 07 



I 



4 



4 

 26 



87 

 116 



58 



30 



60 

 trace 

 trace 

 trace 

 trace 



nil 



These results are, in general, the same as those reached 

 before. The tendency or ability to accumulate manganese 

 varies quite definitely in different genera and species. The 

 present data show, however, more clearly than was then possible 

 that locality has a considerable influence, especially in some 

 species. The chief difficulty in getting clear-cut results on 

 this point arises from the fact that the same locality does not 



1921 April 1 



