316 BONY STRUCTURE OF CRINOIDEANS. 



cal importance among the earliest inhabitants of the ancient 

 deep.* The extensive range W'hich it formerly occupied 

 among the earliest inhabitants of our Planet, may be esti- 

 mated from the fact, that the CrinoYdeans already discovered 

 have been arranged 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 bonesjf a mechanism which shows them all to have 

 formed parts of a well-contrived and delicate mechanical 

 instrument; every part acting in due connexion with the 

 rest, and all adjusted to each other with a view to the per- 

 fect performance of some peculiar function in the economy 

 of each individual. 



The joints, or little bones, of which the skeletons of all 

 these animals were composed, resemble those of the star- 

 fish : their use, hke that of the bony skeleton in vertebral 

 animals, was to constitute the solid support of the whole 

 body, to protect the viscera, and to form the foundation of 

 a system of contractile fibres pervading the gelatinous in- 

 tegument with which all parts of the animal were invested.J 



The bony portions formed the great bulk of the animab 

 as they do in star-fishes. The calcareous matter of these 

 little bones was probably secreted by a Periosteum, which 



* The monograph of Mr. Miller, exhibiling the minute details of every 

 variation in the structure of each cotnponcnt part in the several Genera of 

 the family of Crinoidea, affords an admirable exemplification of the regu- 

 larity, 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. 



I As the contractile fibres of radiated animals are not set together in 

 the same complex manner as the true muscles of the higher orders of ani- 

 mals, the term Muscle, in its strict acceptation, cannot with accuracy be 

 applied to Crinoideans ; but, as most writers have designated by this term 

 the more simple contractile fibres which move their little bones, it will be 

 convenient to retain it in our descriptions of these animals. 



