48 
tlons or heads,* some nearly the shape and size of a 
moderate lemon ; the branches about half an inch thick, 
with five or more calcedonic tubes filled up with flint, 
&c. the rest being chiefly horny looking flint, which with 
some difficulty separates from the green sandy and flinty 
marly mixture. Pectens, &c. are frequently included 
with them. 
The green sand in which this is found owes its name to 
particles of Chlorite, or earthy Talc, coloured green 
by Iron mixed with it,f a colour seldom found in Mica, 
and never imparted by it to the sandstone, of which it 
may form a part. 
* Since my paper on this was read to the Linnean Society, more spe- 
cimens have been found in the Warminster green sand, by Miss Benett, 
indicating many swelling terminations or heads, hydra-like. 
f The Fullers* Earth, near Woburn, is often accompanied by a bright 
§re^n sand, whose colour is occasioned by Iron, it is said. 
