distribution of fossil crinoideans. 419 
^iestined to find their nourishment by spreading 
^heir nets and moving their bodies through a 
®*ted space, from a fixed position at the bottom 
li 
the sea ; or by employing the same instru- 
^iients, either when floating singly through the 
t'^ater, or attached, like the modern Pentelasmis 
^tiatifera, to floating pieces of wood. 
Although the representatives of Crinoideans 
our modern seas are of rare occurrence, 
^^tis family was of vast numerical importance 
ainong the earliest inhabitants of the ancient 
deep.* The extensive range which it formerly 
Occupied among the earliest inhabitants of our 
^anet, may be estimated from the fact, that the 
Crinoideans already discovered have been ar- 
raiiged in four divisions, comprising nine genera, 
l^ast of tliem containing several species, and each 
^•idividual exhibiting, in every one of its many 
riioiisand component little bones, t a mechanism 
'''hich shows them all to have formed parts of a 
'''^ll-contrived and delicate mechanical instru- 
*^ent ; every part acting in due connection with 
The monograph of Mr. Miller, exhibiting the minute details 
^ every variation in the structure of each component part in the 
ral Genera of the family of Crinoidea, affords an admirable 
tv P**fieation of the regularity, with which the same fundamental 
*iiat ** Hiaintained through all the varied modifications 
*^onstitute its numerous extinct genera and species. 
These so-called Ossicula are not true bones, but partake of 
i • of the shelly Plates of Echini, and the calcareous 
of Star-fishes. 
