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generate, was easily to be foiuid and for the rest too the matter is the 

 same as in Anodonta. I can deal with Bucciiium and Fusus together. 

 I had 4 Buccinum and 1 Fusus, which all showed the same burst, not 

 only on the same spot, but they also had the same line of bursting. In 

 these shells 1 always found the last greatest winding near the mouth 

 over its whole width, broken in a rather zig-zag-line. How can it be 

 explained that all the 5 shells had been damaged so heavily and exactly 

 in the same way? I do not know what to answer to this, but I venture 

 to suppose, that the strong pincers of Cancer pagurus, which, as is 

 known, can quite easily crack these shells and feed on the inmates of 

 them, are no strangers to this. But, as all the shells have been regene- 

 rated beautifully and very firmly, the crab must, through the merest 

 chance, have left its prey in the lurch. In 1 Buccinum a hole had been 

 pressed also in the second winding. The regenerate is so perfect that 

 it is hardly to be seen on the inside. However it is so much the better 

 to be seen on the outside. The zig-zag-lines of bursting are very sharply 

 marked and contain long connected scales of the secondary periostracum, 

 while the primary periostracum of the shells has been worn almost every- 

 where. After the bursting, the growth of the shells has further had its 

 normal course. We sometimes find that the lines of growth of these 

 shells, near the mouth are very strongly developed, and rise like crests. 

 These crests of growth must be sharply distinguished from possible 

 lines of bursting. The superficial resemblance is sometimes very great. 

 I have one shell of Mactra stultoriun and one of Solen ensis with rege- 

 nerates. Both regenerates are small and complete: in Mactra on the edge 

 of the shell and in Soien in the middle. The regenerate of Mactra is by 

 far the finest and exactly as in Anodonta^ I have been able to find all the 

 three layers in the regenerate. In all respects the case is the same as in 

 Anodonta, to which I can therefore refer. I only want to draw the atten- 

 tion to the fact that I found in Mactra again ''the crust of lime on the 

 periostracum of the regenerate", exactly as mAnodoiita\ see page 577 and 

 578 of my first communication on this subject. So it seems that in a 

 typical regenerate, this "crust of lime" has to be there and that it is 

 always on the new periostracum on the outside. So the fresh-water 

 shells and the sea-shells regenerate in the same way, though I admit 

 that more material for examination is still desirable. The regenerate 

 of Solen is too unimportant for us to say much about. The newly-for- 

 med periostracum has been worn for a great part, while on the outside 

 of the piece that has been saved, the "crust of lime" is again to be seen, 

 but this crust too has been much damaged by the breakers, and is only 

 slightly developed. - — 



E otter da in. February 22nii 1913 



