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 bones, 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 
gelatinous integument with which all parts of 
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 
Crino'ideans. Our PI. 47, Fig. 2, a. represents 
a reparation near the upper portion of the stem 
of Apiocrinites Rotundus. 
* As the contractile fibres of radiated animals are not set toge- 
ther in the same complex manner as the true muscles of the higher 
orders of animals, the term Muscle, in its strict acceptation, can- 
not with accuracy be applied to Crino'ideans ; 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 m 
our descriptions of these animals. 
