9 



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has continued from the formation of the lyas to our times, and is now met with, 

 though very rarely, in a recent state. The APIOCRINITES ROTUNDUS is only found 

 adhering to a bed of the oolite formation, and the APIOCRINITES 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 arras and fingers surrounding the mouth, prove their affinity to them 

 and the STELLERID^E. 



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 dif- 

 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 lo a regular muscular system. 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 ossicula, it may be 

 proved that the gelatinous integument investing': them possessed muscular 

 powers, and was able to produce effects resulting from muscular action. The 

 movement of the aims, 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, arid I think in some instances had the power of reabsorbitig it. 



c 



