MORPHOLOGICAL PART. 49 
one, except in a very few cases. In the Hudson River group of Cincin- 
nati we occasionally find crinoidal disks, attached to pieces of coral, which 
closely resemble the dorso-central of Antedon. These disks have a pit or 
depression at the middle of the upper face, sometimes enclosing a small 
stem joint. They are irregularly round, and some of them have small pro- 
cesses passing outward from the sides, which seem to represent primitive 
cirri (Plate I. Figs. 9, 10). It is now worthy of note, that we find in 
the same beds some remarkable crinoidal stems, with their lower ends wound 
around some stem fragment or other object, almost as neatly as thread 
upon a spool, the column gradually tapering as it coils, and becoming very 
small at the end.* It has always seemed to us that these stems and the 
terminal plates belonged together, and were separated during the life of the 
Crinoid. Detached roots are found in considerable numbers at Burlington 
and Waldron, and in almost every case the root parted from the stem a little 
above the radicular cirri; but it is curious that hardly ever are parts of 
the crown found associated with them. From these facts we may infer that 
the stem, at least in some cases, became detached from the root, so that the 
Crinoid could change its place of attachment. . A detachment of this kind 
actually took place in a large number, if not in all, recent Pentacrinide, as 
shown by Sir Wyville Thomson,} P. H, Carpenter, and others. The former 
describes this structure in Pentacrinus Wyville-Thomsoni as follows: “All the 
stems of mature examples of this species end inferiorly in a nodal joint 
surrounded by its whorls of cirri, which curve downwards into a kind of 
grappling root. The lower surface of the terminal joint is in all smoothed 
and rounded, evidently by absorption, showing that the animal had for long 
been free. I have no doubt whatever that this character is constant in the 
present species, and that the animal lives loosely rooted in the soft mud, 
and can change its place at pleasure by swimming with its pinnated arms; 
that it is, in fact, intermediate in this respect between the free genus 
Antedon and the permanently fixed Crinoids.” Carpenter found a number 
of other species of Pentacrinus, and some of Metacrinus, in the same condition. 
Roots apparently of Pentacrinus, and belonging to mature or almost mature 
specimens, are occasionally found on telegraph cables, but so far as we know, 
minus the crown and main part of the stem; and it is quite probable that 
all Pentacrinidz were able to detach themselves and float about. 
* S.A. Miller: Journ. Cincin. Soe. Nat. Hist., Vol IIT. Plate 7, Fig. 34. 
+ The Depths of the Sea, pp. 442-444. 
7 
