322 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



Speaking of the rosettes of all the comatulids in which he knew them, P. H. 

 Carpenter says: "The inflected margins of these five radial spoutlike processes 

 are applied to the similarly inflected margins of the dorsal half of the axial radial 

 furrow, lying between the two apertures of the central canal on the internal face 

 of each radial. In this manner a complete radial canal is formed which terminates 

 on the dorsal surface of the radial pentagon, or becomes closed before it reaches the 

 dorsal surface by the union of ingrowths developed from its walls. Besides this very 

 ultimate union between the peripheral portion of the rosette and the internal faces 

 of the radials, its central portion is also frequently connected with the radial penta- 

 gon by delicate processes which sometimes sprout forth irregularly from the inner 

 margins of the component pieces of the latter, but sometimes form a more regular 

 ingrowth which considerably contracts the central space on the ventral aspect of 

 the disk and becomes continuous with an annular projection from the ventral face 

 of the rosette." 



Of the basals at their maximum development in Antedon bifida,W. B. Carpenter 

 writes: "At the beginning of the free stage the circlet of basals, which for the most 

 part is concealed externally by the centrodorsal, is found, when exposed by the 

 removal of the latter, to differ very little either in size or aspect from the circlet first 

 completed in the pentacrinoid. The form of each plate is an irregular trapezoid with 

 its lower angle truncated, and it still retains the solid pellucid margin which origi- 

 nally characterized it. But it has undergone a remarkable thickening by an endog- 

 enous extension of its calcareous network, and this has taken place in such a manner 

 as to leave its substance channeled out by a canal which commences at its lower 

 truncated angle and almost immediately bifurcates, the two branches diverging in 

 such a manner as to pass toward the two radials which severally abut on the sides of 

 the upper triangle of each basal. This canal gives passage to a large sarcodic cord 

 that proceeds from the wall of the chambered organ. Each of the five primary 

 cords (which originally lay on the internal surface of the basals forming the floor 

 of the calyx) subdivides into two branches within the basal whose canal it enters, 

 and thus each of the radials receives two branches supplied to it through the two 

 basals upon which it rests." 



Eegarding the formation of the rosette he says: "The mode in which the 

 rosette is formed by the remodeling and subsequent coalescence of the five basals, 

 and in which the sarcodic extensions of the central axis, which are transmitted 

 through the radials to the arms and pinnules, come to lie on the dorsal or external 

 face of the rosette, is as follows: The cribriform plate of which each basal at first 

 entirely consisted is so much thickened by endogenous growth during the later 

 stages of pentacrinoid life that the radial sarcodic cords come to be entirely invested 

 by calcareous reticulation; and the floor of the ventral cavity shows no inequality 

 as we pass from the central portion formed by the basals to the peripheral formed 

 by the radials. Very soon after the detachment of the young Antedon, however, 

 a remarkable change begins to show itself in the basal pentagon, which is now 

 entirely concealed externally by the extension of the centrodorsal over its dorsal 

 surface; for the cribriform film of which each basal plate was originally composed, 

 and which still forms its external layer, now undergoes resorption, especially where 



