46 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
that the peripheral canals of Cupressocrinus, which consist variously of three, 
four, or five separate passages, correspond to the peripheral vessels of Denta- 
crinus, Rhizocrinus, and other recent Crinoids. He directed attention to the 
fact that there is among different individuals of the same species considerable 
variation in the isolation of these vessels. In some species, in which the 
canals appear to be continuous, there is but one large tri- or tetra-partite 
perforation at the base of the calyx and throughout the stem, which he 
thinks enclosed the four, five, or six separate vessels of other specimens. 
This may be so, although we cannot quite understand how the three or four 
peripheral canals, where they exist, can be extensions of a quinquelocular 
organ. 
The variation in the size of the axial canal among Paleozoic Crinoids is 
most remarkable. In Platycrinus the canal is sometimes no larger than the 
point of a needle; while in Baryerinus, Crotalocrinus, Enallocrinus, Megistocriuus, 
Periechocrinus, ete., it is often from one half to even three fourths the width 
of the joints, and is either round or pentangular. In some of them the walls 
within appear as if built up of thin laminz with spaces between, sometimes 
pectinated and variously sculptured, producing a great multiplication of 
exposed surfaces. In Barycrinus, with a quinque-partite stem, and a sharply 
stellate canal, of which the projecting angles are directed radially toward 
the suture lines, the trigonal inward extensions of the canal are pierced 
by one or more rather large pores, which pass through the body of the 
plates, so as to enter the outer faces of the stem, as shown on Plate I. 
Figs. 6 and 8 a, 6. Five other series of pores follow the longitudinal suture 
lines, and these also communicate with the central canal. 
In the Crotalocrinidx and Periechocrinites, in which the central cavity is 
proportionally still larger than in Barycrinus, the inner structure appears to 
have been less complex ; but its extreme size in both groups, compared with 
that of other Crinoids, and especially with recent ones, seems to imply that it 
was not a mere axial canal, but performed additional functions. 
We have in our collection the root of a large Barycrinus (Plate I. 
Fig. 7), which must have been attached to a smooth, solid substance, for 
the lower surface of the root is perfectly flat. In this root only two of the 
five primary branches were developed, and these are but partly preserved, 
but enough is seen to show that they had been placed on a level with the 
truncated lower face of the main trunk. The development of the other 
three cirri seems to have been checked by contact with the bottom, but their 
