446 THE DEPTHS OF THE SEA. [cHaP. Ix. 
the radial axillary originates a simple arm only from 
one or both of its sides, thus reducing the total 
number of the arms; and sometimes one of the four 
arms given off from the brachial axillaries again 
divides, in which case the total number of arms is 
increased. The structure of the disk is much the 
same as in the species of the genus previously known. 
‘wo other fixed crinoids were dredged from the 
‘Porcupine,’ and these must be referred to the Apio- 
erinide, which differ from all other sections of the 
order in the structure of the upper part of the stem. 
At a certain point, considerably below the crown of 
arms, the joints of the stem widen by the greater 
development of the calcareous ring, the central 
tube only increasing very slightly in width. The 
widening of the stem-joints increases upwards until 
a pear-shaped body is produced, usually very elegant 
in form, which, looking from the outside, one would 
take for the calyx. It is, however, nothing more 
than a symmetrical thickening of the stem, and the 
body-cavity occupies a shallow depression in the top 
of it included within the plates of the cup—the 
basals and radials—which are thicker and more 
solid than in other crinoids, but otherwise normally 
arranged. The stem is usually long and simple 
until near the base, where it forms some means of 
attachment, either as in the celebrated pear-encrinites 
of the forest marble, a complicated arrangement of 
concentric layers of calcareous cement which fix it 
firmly to some foreign body, or, as in the chalk 
Bourguetticrinus and in the recent Rhizocrinus, an 
irregular series of jointed branching cirri. 
The Apiocrinide attained their maximum during 
