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the state of preservation, as it often disguises some 
characters while it discloses others useful to the Geolo- 
gist. 
The specimen figured is from Whitby, it was lent me 
by Colonel Birch, I possess a fragment of an equally 
large one for which I am indebted to the generosity of 
the Marchioness of Bath, it is interesting inasmuch as it 
shews that in the very young shell the septa are much less 
sinuated ; I have also one about two inches in diameter in 
which the septa are perfectly formed. I believe they 
both came from Whitby. 
