420 BONY STRUCTURE OF CRINOIDEANS. 
the rest, and all adjusted to each other with a 
view to the perfect performance of some peculiar 
function in the economy of each individual. 
The joints, or little hones, of which the skele- 
tons of all these animals were composed, resemble 
those of the star-fish : their use, like that of the 
bony skeleton in vertebral animals, was to con- 
stitute the solid support of the whole body, to 
protect the viscera, and to form the foundation of 
a system of contractile fibres pervading the gela- 
tinous integument with which all parts ot the 
animal were invested.* 
The bony portions formed the great bulk of the 
animal, as they do in star-fishes. The calcareous 
matter of these little bones was probably secreted 
by a Periosteum, which in cases of accident, to 
which bodies so delicately constructed must have 
been much exposed in an element so stormy aS 
the sea, seems to have had the power of deposit- 
ing fresh matter to repair casual injuries. Mr- 
Miller’s work abounds with examples of repara- 
tions of this kind in various fossil species of Cn- 
noi'deans. Our PI. 47, Fig. 2% represents a re- 
paration near the upper portion of the stem e 
Apiocrinites Rotundus. 
* As the contractile fibres of radiated animals are not set toge- 
ther in the same complex manner as the true muscles of thehigl’®'^ 
orders of animals, the term Muscle, in its strict acceptation, cao^ 
not with accuracy be applied to Criuoideans ; but, as most wU 
ters have designated by this term the more simple contrac 
fibres which move their little bones, it will be convenient to r 
tain it in our descriptions of these animals. 
