162 
notice as it gives rise to beautifully polished oblong cones, 
which frequently remain after the shell is decomposed, and 
which have often puzzled Collectors, from the difficulty of 
ascertaining what they belong to. They are from Folkstone 
in Kent, by favour of Mr. Gibbs. 
DENTALIUM costatum. 
TAB. L XX.— Fig. 8. 
Spec. Char. Surface marked with twelve or more 
closely set ribs; lines of growth obscure; 
aperture circular. 
The ribs and sulci between them are nearly equal and 
rounded. 
I am greatly indebted to Mrs. Cobbold for sending me 
this rarity from the Holywell Craig, which place has 
afforded to ingenuity of enquiry and research such fine 
and instructive specimens, of which many are yet to come. 
It is but little changed, and seems like those shells that have 
been softened by exposure to the weather, then rolled a 
little, and afterwards preserved in Ochraceous Gravel. 
It does not agree with any recent species I know of. 
