of Edinburgh, Session 1871 - 72 . 
771 
This variability in so important a character, particularly when 
associated with so great a preponderance in bulk of the vegetative 
over the more specially animal parts of the organism, must un¬ 
doubtedly be accepted as indicating a deterioration from the 
symmetry and compactness of the Apiocrinidge of the Jurassic 
period. 
The anchylosed ring of first radials is succeeded by a tier of free 
second radials, which are united by a straight syzygial suture to 
the next series—the radial axillaries. The surface of the funnel- 
shaped dilation of the stem, headed by the ring of first radials, is 
smooth and uniform, and the second radials and radial axillaries 
present a smooth regularly arched outer surface. The radial 
axillaries differ from the corresponding joints in most other known 
crinoids in contracting slightly above, presenting only one arti¬ 
culating facet, and giving origin to a single arm. The arms, which 
in the larger specimens are from 10 to 12 mm. in length, consist of 
a series of from about twenty-eight to thirty-four joints, uniformly 
transversely arched externally, and deeply grooved within to 
receive the soft parts. Each alternate joint bears a pinnule 
alternating on either side of the axis of the arm, and the joint 
which does not bear a pinnule is united to the pinnule-bearing 
joint above it by a syzygy: thus joints with muscular connections 
and syzygies alternate throughout the whole length of the arm. 
The pinnules, twelve to fourteen in number, consist of a uniform 
series of minute joints united by muscular connections. The grooves 
of the arm and of the pinnules are bordered by a double series of 
delicate round fenestrated calcareous plates, which, when the animal 
is contracted and at rest, form a closely imbricated covering to the 
nerve and the radial vessel with its delicate cmcal tentacles. The 
mouth is placed in the centre of the disk, and radial canals, equal 
in number to the number of arms, pass across the disk, and are 
continuous with the arm grooves. The mouth is surrounded by a 
row of flexible cirri arranged nearly as in the pentacrinoid of 
Antedon , and is provided with five oval calcareous valve-like plates 
occupying the interradial angles, and closing over the mouth at 
will. A low papilla in one of the interradial species indicates the 
position of the minute excretory orifice. 
Rhizocrinus lofotensis is a very interesting addition to the British 
