MORPHOLOGICAL PART. 39 
about three feet, —one, not quite complete, being that of a large Megistocrinus 
Evansi, the other, which is perfect, of a Strotocrinus regalis, two of the largest 
known species. That seems to have been about the maximum length, and 
it may be safely asserted that the stem in the majority of the older Crinoids 
was not much over a foot long. Some stems are proportionally wider at the 
top, and taper all the way to the root; others are larger at the distal end 
than at the proximal; while still others are widest in the middle. 
The root is even more variable. Its form was evidently accommodated 
to the conditions of the place of its attachment. When attached to a solid 
substance, it was flattened at the distal face, the radicular cirri spreading 
out horizontally; but when growing on an oozy bottom, it gave off long 
vertical and lateral branches, entering the mud. 
The stem is either circular, elliptic, pentangular, stellate, semilunate, or 
quadrangular, changing from angular to round on approaching the root. It is 
composed of joints, which vary often considerably in size. Certain of these 
joints, which have been denominated “ nodal” joints, are separated from each 
other by intervals of different lengths, which are filled by internodal growth. 
The nodal joints are not only longer than the internodal ones, but also 
wider, and, as a rule, increase in Jength downward. Their diameter is 
greatest in the upper part of the stem, where in some species of the Came- 
rata it is often twice, and exceptionally three times, that of the internodal 
joints. The projecting margins are sometimes knife-like, the edges occa- 
sionally crenulated, spinous, or nodose. The greater amount of length 
which characterizes these joints, however, does not extend to their full 
thickness, but is more or less restricted to the projecting margins, the 
middle part at both ends being depressed, so as to enclose wholly or in 
part the adjacent internodals. 
In the growing Crinoid, the stem constantly increased in length by the 
production of new joints, introduced either directly beneath the calyx, or at 
some distance from it. The joints which are formed at the proximal end of 
the stem gradually developed into nodal joints, and all those intervening 
comprise the internodal joints. The nodal joints of the Inadunata and 
Camerata, and also of many of the later and recent Crinoids, were intro- 
duced directly beneath the basals and infrabasals respectively, so that the 
uppermost joint was always the youngest joint of the stem. But in the 
young Comatula, in which the top joint subsequently develops into a centro- 
dorsal, in the recent Mesozoic Millericrinus, and probably in the recent Rhizo- 
