766 Proceedings of the Royal Society 
from the joint, turning down hooklike towards the tips. Each 
cirrus consists of about 36 joints. The nodal joint, that is to say 
the joint modified for the insertion of the cirri, is single; but it is 
united to the joint beneath by a peculiar suture with much of the 
character of a syzygy, Most of the examples of P. asteria which 
have reached Europe have had the stem recently broken. In one 
however in my possession, the stem, which is unusually short, had 
evidently given way at one of these joints long before the death of 
the animal, for the surface of the terminal joint is smoothed and 
rounded, and the terminal row of cirri are curved over it. This 
example, at all events, must have lived for some time free. 
In Pentacrinus asteria , the basal plates of the cup project like 
small round buttons over the ends of the salient angles of the first 
stem joint. The first radials are connected with the second radials 
by a true joint with muscles and ligaments, and the second radial is 
united to the radial axillary by a syzygy. There are from 70 to 120 
pinnated arms. There is constantly a syzygy on each branch at the 
first joint beyond each bifurcation, but there are few syzygies on 
the arms after their last bifurcation, although in some specimens 
one is met with here and there. 
All the examples of P. asteria in European museums have lost the 
soft parts and the disk; but I have one example which is com- 
plete. The mouth is central, and five radial grooves pass from the 
edge of the mouth-opening to the proximal ends of the arms, and 
become continuous with the brachial grooves, dividing with each 
bifurcation. The perisom of the disk is covered with irregular 
calcareous plates, and at the free inner angles of the interradial 
spaces these plates become closer, and form a solid kind of boss ; 
but there are no distinct oral plates. A rather long anal tube 
occupies the centre of one of the interradial spaces. 
Pentacrinus mulleri , CErstedt, seems to be more common than P. 
asteria especially off the Danish West Indian Islands. The whole 
animal is more delicate in form. The stem attains nearly the 
same height, but is more slender. The nodes occur about every 
twelfth joint and at every node two stem-joints are modified. The 
upper joint bears the facets for the insertion of the cirri, and the 
second is grooved to receive the thick basal portions of the cirri, 
which bend downwards for a little way closely adpressed to the 
