DISTRIBUTION OF FOSSIL CRINOIDEANS. 419 
destined to find their nourishment by spreading 
their nets and moving their bodies through a 
limited space, from a fixed position at the bottom 
of the sea ; or by employing the same instru- 
ments, either when floating singly through the 
water, or attached, like the modern Pentelasmis 
anatifera, to floating pieces of wood. 
Although the representatives of Crinoideans 
in our modern seas are of rare occurrence, 
this family was of vast numerical importance 
among the earliest inhabitants of the ancient 
deep.^ The extensive range which it formerly 
occupied among the earliest inhabitants of our 
Planet, may be estimated from the fact, that the 
Crinoideans already discovered have been ar- 
ranged in four divisions, comprising nine genera, 
most of them containing several species, and each 
individual exhibiting, in every one of its many 
thousand component little bones,! a mechanism 
which shows them all to have formed parts of a 
well-contrived and delicate mechanical instru- 
ment ; every part acting in due connection with 
* The monograph of Mr. Miller, exhibiting the minute details 
of every variation in the structure of each component part in the 
several Genera of the family of Crinoidea, affords an admirable 
exemplification of the regularity, with which the same fundamental 
type is rigidly maintained through all the varied modifications 
that constitute its numerous extinct genera and species. 
t These so-called Ossicula are not true bones, but partake of 
the nature of the shelly Plates of Echini, and the calcareous 
joints of Star-fishes. 
