181 
TAB. CCXCI. 
SILEX Quartzum coralliformis. 
Coralliform Flint. 
Div. 2. Imitative, 
eee 
Tus is one of the most beautiful, and perhaps local, 
of the Flint Coral formations, and is found in tolerable 
abundance in a field near Tidsbury, Wiltshire, in pieces, 
sometimes as large as a quartern loaf. Some specimens 
show the remaining form of a real Coral most perfectly ; 
having at the same time little globular infiltrations, as if in 
the act of filling the spaces of the Coral with a whitish 
calcedony or cachalong-like substance, which more solidly 
pervades the Flint in other parts; and again a considerable 
part of the petrifaction is in so solid a state, that it retains 
a great degree of semitransparency, and either the reticu- 
lated or stellated structure ; or both remain distinguished by 
the whitish opaque Calcedony, so beautifully, that it is one 
of the most curious subjects that I know of for orna- 
mental jewellery. I have most of the varieties here figured 
as one speciinen, but not on the same piece. Besides the 
stony representation of a Coral, perhaps new to our cata- 
logue, there often remains the oval hole of the Mytilus or 
Pholas, which are known to bore holes in old Corals and 
various rocks. 
I am obliged to my good and very generous friends, 
Thomas Mead and William Cunnington, Esquires, for 
most of my specimens of this curious modification of Flint, 
