ACTINOPODOUS HOLOTHUllIOIDEA. 



15 



one or more of tho arms may be branched, the branching 

 always taking place dichotomously. Only very rarely, and 

 then mostly on ambulacral appendages, there may exist four- 

 armed spicules, the arms being at right angles with one 

 another. From the centre of the triradiate basal disk, there 

 arises a single pillar. The base never shows a trace of four pillars, 

 but the pillar arises as a single monolith. It hardly tapers at 

 all. Sometimes it becomes slightly thicker toward the upper end. 



Textfig. 2, 



SijnaU.ades iriradiala : 

 a — Calcareous ring ; h, c 

 — Table-like bodies of 

 dorsal per-'some; d — Same 

 of \ entrai pcrisome ; e — 

 Supporting rod of dorsal 

 papilla ; /, q — Same of 

 ventral pedicels, {h—ij 

 X IGO). I — loterradialia ; 

 R — Kadiulia. 



At the upper end, the })illar terminates after first becoming divided 

 into several points ; or these points may be united by cross-junc- 

 tions, leaving perforations between them. These table-like deposits 



