ae 
FOSSIL CRINOIDEA. 283 
pentapetalous striations. There are numerous side-arms sent 
off from the column in groups of five, at uncertain distances. 
The mouth is situated in the centre of a plated inte- 
- gument spread over the top of the receptacle. The arms, 
_ which arise from the margin of the latter, surround the 
_ mouth, and when spread out, with their numerous pinne 
or feelers expanded, form a net for the capture of prey ; 
and are the organs by which the animal obtains food, and 
conveys it to the mouth. 
Fossiz CrinomEsa.—The fossil crinoids, like the recent pro- 
totype above described, consist of an articulated column, and 
a receptacle formed of calcareous plates, and articulated arms 
or tentacula. They constitute two groups ; the Hncrinites, 
in which the ossicula of the column are subcylindrical and 
smooth ; and the Pentacrinites, with a stem composed of 
pentangular ossicles, as in the living Pentacrinus. 
The petrified remains consist of the ossicula of the column, 
arms, and tentacula; of the plates of the receptacle ; and 
of the peduncle, or process of attachment by which the 
animal was fixed to the rock. The peduncle is in some 
species flat and expanded, like that of the Gorgonia ; in 
others, it consists of long jointed processes. These several 
parts are commonly found detached, and intermingled with 
detritus in the strata ; throughout extensive beds of encrinital 
marble, vestiges of the receptacle are but seldom discover- 
able. In some localities the skeletons are preserved entire, 
and lie expanded on the surface of the layers of shale, clay, 
or limestone, as if the animals had been enveloped by the 
soft deposit when alive in their native seas. 
These remarks will serve to convey a general idea of the 
nature of the crinoidal remains which are scattered through 
certain rocks in such inconceivable quantities ; for, much as 
the columns may differ in form, the ossicula in their mark- 
ings, and the plates of the receptacle in their configuration 
