9 
has continued from the formation of the lyas to our times, and is now met with, 
though very rarely, in a recent state. The AProcniNITES ROTUNDUS is only found. 
adhering to a bed of the oolite formation, and the A PIOCRINITES ELLIPTICUS in 
chalk. 
It also appears that many species of Crinoidea have been very generally 
distributed over our earth, whilst others (at least as far as our knowledge ex- 
tends) were more local. 
Observations. 
The essentially distinguishing character of, the family of Crinoidea, is the 
column formed of numerous joints which separates them from the Polypi, 
whilst the arms and fingers surrounding the mouth,-prove their affinity to them 
and the STELLERIDE, : jl 
The integuments of the Crinoidea appear to have had the power of forming - 
by secreting a number of calcarious concretions, forming joints or ossicula, 
composing what may be termed the skeleton of the animal. These can- 
not, indeed, with strict propriety, be termed bones, since that denomina- 
tion is almost limited by usage to the parts constituting the skeleton of ver- 
tebral animals, whereas the ossicular concretions of the Crinoidea in many 
points (and probably also in their chymical composition) bear a nearer analogy 
to the plates of the Echinus and the joints of the Star-fish. Yet entirely በ 
ferent both in disposition and arrangement, as are these ossicula from the 
bones of vertebral animals, they manifestly are intended to subserve the same 
general uses, to form the solid support of the whole body, to protect the 
viscera, and as we shall presently see reason to believe, to form the basis 
of attachment to a regular muscularsystem. Having thus guarded my use of 
the term ossicula against the misapprehension or objections that might other- 
wise possibly arise, I shall, without scruple, employ that appellation to desig- 
nate these bodies. By the depressions and foramina in the ossicnla, it may be 
proved that the gelatinous integument investing: them possessed muscular 
powers, and was able to produce effects resulting from m uscular action. The 
movement of the arms, the fingers, and tentacula, could only have been effected 
in this manner. 
A Periosteum seems to have secreted and arranged the calcarious matter 
of the ossicula, and I think in some instances had the power of reabsorbing it. 



