ftones are all perfedly formed ; they differ not in figure one 
from another, but that fome have their fides a Httle depref- 
fed : upon a few of them there adhered a httle portion of a 
glittering mineral like Iron, which Mr. L^/^er hath often ob- 
ferVed, item concJntes flurium generum^ ahaq-^ midta fofjilia fyrite tn- 
fe^a^ de Font, Me J, cap* ^p-^o, I put fome of them into Vine- 
negar where they made a ftrong and a boyling efiervef- 
cence. 
The Bivalvular are moft of them no bigger than a kidney 
Bean, fome leflfer, a few as broad as the largeii fort* of Beans, 
but the valve much thinner than any of that kind, which 
had been the Exuviae of an Animal, the gibbous part of the 
valve is fmooth, and of the fame colour with that of 
the turbinated. In a few there are fome oblong lineations 
bent circularly to the commiffure of the valve : I have a 
piece of fuch a one by me confifting of feveral LamdU^ which 
hath this further obfervable in it, that the gibbous part is 
of a moft beautiful black fhining colour, and the inner part 
of a fhining pearl coloured fubftance. 
Of this bivalvular fort many of them feem to be in fieri ^not 
as to their fhape but as to their hardnels and thicknefs, there 
being in fome only the prima fiamtna^ and in others, the feveral 
fteps and progrefTes toward a perfed: Figuration, which feems 
to me an unanfwerable Argument, for their never having 
been the fpoils of Animals Some of thefe appeared in the 
inner fide white, and it came off upon the fingers like Chalk, 
and feemed as if a depreflion had been firft made in the bed, 
of the fhape of a valve, and then the convex fide rubbed 
with Ghaik or painted white- 
Thofe pieces of thisoddconcretion which I keep by mefnow 
the Mar], which is in the interilices, is grown hard ) appear 
much like that courfe fort of Marble-itone which is dug a- 
but PluckUj ill the Wild of Kent. Which Marble leems to be 
a coagmentation of fuch fhelj-like ftones, the Marl betwixt 
them having acquired a firm fohdity and hardnefs. With 
this ftone they make their Caufeys in that part of 
the County : and they are apt to be worn into little cavities, 
or holes, where they have lain long expofed to the Air ; the 
rains in length of tim^ wafhing away the portions of Marl 
I which is lefs hard th^n the reft j from the orifices and in- 
rerfticcs of thofe fhelHike ftones. 1 am much confirmed in 
this Opinion by a piece of Marble, mlaid as it were with 
