MONOGRAPH OF THE EXISTING CEINOIDS. 565 



the column. These were also a little broader or thicker than those following, 

 which were cylindrical, becoming more and more elongate toward the middle of the 

 column, where they were from six to seven times as long as broad. Toward the 

 distal end of the column the segments became shorter again. With the exception 

 of the two or three proximal columnals and of the distalmost, all showed a narrow 

 median transverse line, sometimes slightly elevated, denoting the primitive annulus. 

 The distal end of the terminal segment spreads out into a little hyaline disk, almost 

 circular, which is attached by its lower face to the foreign body. This disk is 

 almost entirely composed of a fine calcareous network, a continuation of that of 

 the segment itself, irregular and lobed in outline. 



The crown is composed entirely of the basals and orals, no trace of the radials 

 having appeared, and no infrabasals having been identified. 



The straight distal border of the basals is not quite equal to their length ; the 

 two lateral borders converge, so that the proximal border is very short. 



The orals are of about the same size as the basals. 



All the plates of both series are composed of the ordinary calcareous network, 

 moderatelv regular, and pierced with little rounded perforations, which on the 

 rounded (distal) tips of the orals is furnished with minute but prominent conical 

 points. 



Another specimen, taken at the same time and place as the preceding, was 

 attached to the stem of a dead individual, much older, of the same species, which, 

 in its turn, was attached to a branch of a Crisia denticulata. Although this 

 example was no larger than the preceding, being 4 mm. in total length, with the 

 crown 0.5 mm. long, it was a little more developed. 



The column was composed of 19 segments, of which the four or five uppermost 

 were more strongly compressed longitudinally than were the corresponding ele- 

 ments in the preceding, being in lateral view twice as broad as long. The follow- 

 ing were cylindrical and became progressively longer and longer, so that at the 

 middle of the stem they were five or six times as long as broad; here they were 

 somewhat constricted centrally and thickened at the two ends, and at the same 

 time a little narrower than those above and those below. The latter gradually de- 

 crease somewhat in length. 



The end of the distalmost columnal expands into a little disk with a convex 

 surface, from the periphery of which there arise four short, thick, digitiform 

 prolongations, which extend over the surface of the object of attachment (in 

 this case a columnal of a larger individual) and partially inclose it. The disk 

 and its prolongations are composed of a fine calcareous network like that of the 

 columnals but less regular. 



In Antedon the terminal stem plate is a circular or slightly lobed disk instead 

 of a digitiform structure as in this species. 



Between each pair of orals and basals there has been formed a radial, the 

 radials thus separating these plates heretofore united by their bases. 



The basals appear a little smaller than at the preceding stage, and now their 

 distal border, previously straight, forms in the center, on account of the intercalated 

 radials, an obtuse angle. 



