l8 SMITHSONIAN INSTITUTION 



The first developed, or primary, root member usually took the same direc- 

 tion as the original point, and became the largest; it might divide and sub- 

 divide into strong branches at whose axils were formed one or two of the 

 openings and resulting sacs. Two to four other strong root members are given 

 off toward the opposite side of the point of attachment, forming with the 

 former ones the primary sacs; these may be followed by other and younger 

 roots giving rise to successively smaller sacs which lie around the upper 

 periphery of the bulb, but usually do not extend to the middle or lower zone. 



Such a one-sided growth of root branches is not uncommon. It appears 

 in numerous unconsolidated roots of an otherwise unknown crinoid of the same 

 formation; and the same thing occurs in the Recent genera Rhizocrinus and 

 Bathycrinus, and probably in many forms which are fixed to the sea bottom by 

 delicate branching roots (see P. H. Carpenter, Challenger Report, Stalked 

 Crinoids, pi. 7, fig. 1; pi. 9, fig. 1). 



This mode of distribution of the roots may explain the further curious 

 fact that whereas the axial canal in this genus is pentapetalous, the number 

 of principal chambers or sacs in the bulbs is usually not five, but four; addi- 

 tional ones irregularly, and occasionally to a total of 10 or 1 1, may develop 

 from younger roots, as already explained, or from further bifurcations. There- 

 fore, while a cross-section near the stalked end of a bulb may show eight or ten 

 chambers, a section taken toward the other end will usually have but four. 

 This is finely shown by figures 1, 2, 3 of Schuchert's plate 44, giving three hori- 

 zontal sections at different levels in the same specimen, the upper two having 

 eight chambers, while in the lower one the number is reduced to four large 

 chambers with a faint remnant of a fifth. In three other specimens sectioned 

 above the middle there are four large chambers and two small ones. The weath- 

 ered specimen figured by Schuchert on his plate 43, and the section in Hall's 

 figure 8 of his plate 35, show the four primary chambers as they will be found in 

 probably 90 per cent of the specimens at a level in the lower third of the bulb. 

 Hall's figure 1 of the same plate shows how there were four principal lobes, 

 with smaller ones added at the top. They are always unequal; sometimes one 

 is much larger than the rest, and sometimes three are large and one small. 

 Other irregularities are seen in Hall's figures 3 and 7 of his plate 35. Where 

 there is a considerable increase in number of chambers above four or five, it 

 will usually be found that they are developed along the recumbent part of the 

 stem, or the primary member, as a sort of axis, instead of in a symmetric 

 radiation from a central stem. This is excellently shown by Schuchert's 

 figure 3, plate 42, and Hall's figures 1 and 3, plate 35. 



Finally, we have some interesting information as to the growth of the 

 roots, derived from young specimens which have lodged upon the hard surface 

 of mature bulbs and become fixed to it. Being unable in this situation to 



