41 



one of whose points is somewhat truncated. These are so arranged round 

 common centre, towards which their truncated points are directed, as to 

 occupy a small pentagonal area. At their truncated point they iiave a tnfo- 

 liated elevation (similar to, though less conspicuous than that noticed in the 

 former genus) sending off two lateral folds. Below that part of the prlvis 

 which projects beyond the circumference of the column, each joii.t has a small 

 subtubercular swelling, serving it as an abutment, fur tinner adhesion to the 

 first columnar joint. At the exterior circumference tach joint ot the pelvis is 

 angularly truncated, so that a pentagonal circumference is formed, whose sides 

 being somewhat excavated and faintly striated, give adhesion to the first cos- 

 tal joints. 



The FIRST COSTAL JOINTS, (PL. in. fig. 5. to 7.) which enlarge outwards, 

 form by their union a pentagon surrounding that occupied by the pelvis, but 

 inconsequence of the contraction of the four outer marginal edges of these 

 joints, their external surface becomes convex, and in youn. 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 : (PL. n. fig. 3. and 4.) and as the animal grows, they gain 

 still farther room by the extension of the pelvis. 



At the innur truncated point of each first costal joint, it is excavated trans- 

 versely in an angular manner, 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 the superior costal joint of Apiocrinites 

 rotundus, but being infinitely more delicate and elegant. 



The SECOND COSTAL (PL. HI. 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. (Pi, u.) 



