CHAP. IX. ] THE DEEP-SEA FAUNA. 44] 
another bifurcation, and seven or eight joints farther 
on another, and so on, but more irregularly the 
farther from the centre, till each of the five primary 
rays has divided into from twenty to thirty ultimate 
branches, producing a rich crown of more than a 
hundred arms. The upper surface of each arm-joint 
is deeply grooved, the lower arched; and from one 
side of each, alternately on either side of the arm, 
there springs a series of flattened ossicles. These 
form the ultimate branchlets, or ‘ pinnules,’ which 
fringe the arms as the barbs fringe the shaft of a 
feather. Unfortunately, most of the examples of 
Pentacrinus asteria hitherto procured have had the 
soft parts destroyed and the disk more or less injured. 
One specimen, however, in my possession is quite 
perfect. The body is covered above by a membrane 
closely tesselated with irregularly-formed flat plates ; 
this membrane, after covering the disk, dips into 
the spaces between the series of radial joints, and 
with the joints of the cup completes the body-wall. 
The mouth is a rounded opening of considerable size 
in the centre of the disk, and opens into a stomach 
passing into a short curved intestine which ends in 
a long excretory tube,—the so-called ‘ proboscis’ of 
the fossil crinoids,—which rises from the surface 
of the disk near the mouth. From the mouth five 
deep grooves, bordered on either side by small square 
plates, run out to the edge of the disk, and are con- 
tinuous with the grooves on the upper surface of the 
arms and pinnules, while in the angles between them 
five thickened masses of the mailing of the disk 
surround the mouth like valves. These were at 
first supposed to answer the purpose of teeth. The 
