MONOGRAPH OF THE EXISTING CBINOIDS. 



565 



the column. These were also a little broader or tlncker t^^^^^ ^^^^^Vf " '^;;7^' 

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

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

 distal end of the column the segments became shorter agaxn. Wi h 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 l-''^^-^ ;^'^';" "^^ 

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

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

 ahnost 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 

 havincr 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. 



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

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

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



^'''''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 Crhia dentkulata. 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- 

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

 mfddle 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 inc ose it. Jhe disk 

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



columnals but less regular. r u*, i u i r i • * ^ 



In A7itedon the terminal stem plate is a circular or slightly lobed disk instead 



of a digitiform structure as in this species ,. i .u 



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 



di.stal border, previously straight, forms in the center, on account of the intercalated 



radials, an obtuse angle. 



