CRUSTACEA. 
121 
of the Downs, and, under the names of slieplierds’ 
Iielmets and crowns, are preserved by the peasantry 
as ornaments for the rustic sideboard of the cot- 
tage. Tliis class of organic remains is so familiar 
to every one, that it is cpiite unnecessary to give a 
detailed description of the various species that oc- 
cur in the chalk of the south-east of England. 
CRUSTACEA. 
The fossil remains of those species of Cancer, in 
which tlie crustaceous covering is hard and compact, 
are not unfrequent in the London clay at Highgatc, 
Sheppey, &c. ; and a few have been found in the 
Galt of Sussex : but the lobster, cray-fish, and other 
kind, whose structure is more delicate and fra- 
gile, but seldom occur in a mineralized state, and 
rank among the most rare and interesting objects 
in the cabinet of the oryctologist. 
In the chalk near Lewes the claws of a delicate 
species of Astacus are often found, and rarely, por- 
tions of the crustaceous covering of the body. These 
remains consist of a delicate friable crust, and 
when first collected are of a dark chocolate colour, 
inclining to black ; but they become pale, and lose 
much of their beauty, by exposure to the air and 
light. The inner surface only is seen in the speci- 
mens discovered by breaking the chalk ; it is 
glossy, and covered with minute circular depres- 
sions formed by the bases of the spines. The 
external surface is armed with short spines and 
papillm, and is invariably concealed by the chalk 
until the latter be carefully removed : a process 
