41 
one of whose points is somewhat truncated. "These are so arranged round a 
common centre, towards which their truncated points are directed, as to 
occupy a small pentagonal area. At their truncated point they have a trifo- 
liated elevation (similar to, though less conspicuous than that noticed in the 
former genus) sending off two lateral folds. Below that part of the pelvis 
which projects beyond the circumference of the column, each Joint has a small , 
subtubercular swelling, serving it as an abutment, for firmer adhesion to the 
- first columnar joint. At the exterior circumference each joint of the pelvis is 
angularly truncated, so that a pentagonal circumference is formed, whose sides 
being somewhat excavated and 0 striated, give adhesion to the ñrst cos- 
tal joints. 
The Fırsr Cosraz Joints, (Pr. 111. fig. 5. to 7.) which enlarge outwards, 
form by their union a pentagon surrounding that occupied by the pelvis, but 
incons equence of the contraction of the four outer marginal edges of these 
joints, their external surface becomes convex, and in youny specimens 
almost tubercular ; thus, at the junction of the pelvis,* a cavity is left between 
them and the column, sufficient to allow them space for a free power of motion 
in that direction: (Pr. 11. fig. S. and 4.) and as the animal grows, they gain 
«still farther room by the extension of the pelvis. 
At the inner truncated point of each first costal joint, it is excavated trans- 
versely in an angular manuer, the lower side of this angle showing four folds, two 
uniting to those noticed on the pelvis, and two to the lateral surfaces. From 
the subconcave surface, a beautiful highly muscular lip-like process, much 
plicated and scalloped, extends into the abdominal cavity; the centre of this. 
process is excavated so as to lead to a tranverse perforated ridge, thus bearing 
a near analogy to the formation of tlre superior costal joint of Apiocrinites 
rotundus, but being infinitely more delicate and elegant. 
The SECOND Costan (Pr. ru. fig. 8. to 10.) bears great resemblance to the 
former in figure, in the contraction of the margins at. the exterior circumfer- 
ence, and its consequent convexity; being almost tubercular in young spe- 
* The pelvis on account of its smallness is buried in the cavity, and cannot be seen in a 
lateral view. (PL. 11.) à 
5 
