KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 48, N:0 1. 



7 



From these curves we consequently deduce the following results as to the 

 variation of Margarita groenlandica: The typical form and the variety umbilicalis are 

 common in Greenland; var, umbilicalis is the most common form of the species on 

 Spitzbergen and forma typica is occasional; the last is dominant in Iceland and 

 Norway, where var. umbilicalis is very rare. It is also evident, that numerous stages 

 of transition occur between the two forms in Greenland, so that they cannot be 

 distinguished from one another — at least judging solely by their formal characters. 

















































































































































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13 IH 1^ 





































/ 













7^ 















y 

















-f ■ 





it 



J 























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y 







f 





















































Ficr. 4. 



5 6 1 8 1 10 11 



Fig. 5. 























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— 





ä • 











.y 











a 















































































,x 









ay 



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X ■ 





















































5 6 1 

 Fig. 6. 



5 6 1 



Fig. 7. 



Figs. 4 — 7. PiindiirclJa noaehhiu. 4. Southern Scandinavia. 5. Spitzbergen, (i. Greenland. 7. Finmark. 

 O breadth, x lieiglit, • apex perpendicularly from posterior margin. 



In curve 1, the broken line marks the limit between the two forms, which were kept 

 apart from one another when being measured. The line divides the zone into two 

 equal halves, which is intended to indicate that the extreme specimens of the higher 

 part form the variety, those of the lower part the type (in their clearest development), 

 and that they are connected together by intermediate specimens. 



The above curves (4 — 7) illustrate the variation of Punciurella yioacMna. 

 On the X-axis there has been inserted the length (or maximal diameter), on the Y- 

 axis the measurements 1) of breadth (minimal diameter), 2) of height and 3) of the 

 distance perpendicularly from the apex to the posterior margin. 



