334 THE MEDALS OF CREATION. Cuap. IX. 
As the shells of Chalk Echinites, when hollow, are often 
lined with crystals (see Lign. 103, jig. 3), it is worth 
while to break all indifferent specimens of the common 
species, with the chance of obtaining an example of this 
kind. ? 
The chalk must not be scraped off from the crust or 
shell of the Echinites, or the minute granulations and pa- 
pillee will be injured or removed; it should be flaked off 
with a blunt point. 
In friable arenaceous strata, as in some of the Maestricht 
and Tertiary deposits, the Echinites may be extricated in as 
perfect a condition as if fresh from the sea; it is, indeed, 
probable, from the habit of these animals of burrowing in 
mud and sand, that in many instances they were entombed 
alive by the sediment in which their fossil remains are 
imbedded. 
Beautiful Cidarites and their spines may be collected in 
the Oolitic strata at Calne, Chippenham, Bath, &c.; and in 
the coralline Oolite near Faringdon ; and of Saleniz, in the 
Greensand gravel-pits near that town. 
The Upper Greensand near Warminster, and at Chute 
Farm, near Heytesbury, abounds in small Cidaritide and 
other echinites. The large sinuated Clypeus is found in 
great perfection in the Oolite at Malton, Cheltenham, Glou- 
cester, &c. 
The cretaceous echinites are to be met with in most loca- 
lities of the white chalk. The chalk pits in Kent, especially 
at Gravesend, Northfleet, Chatham, &c. are rich in Cidarites, 
and their spines. The Galerites, and Ananchytes, are also 
very fine and numerous; and the softness of the chalk renders 
their extrication from the stone a delightful task for the 
young geologist. 
Specimens of the common kinds of fossil Echinoderms 
may be obtained at moderate prices of the dealers named in 
the Appendix. 
