MONOGRAPH OF THE EXISTING CKINOIDS. 103 



Smooth cirri. — Cirri without dorsal spines or processes on the distal segments (see 

 figs. 312, 313, p. 271, 316, p. 273, 327, 328, p. 281, 340, p. 287, 356, p. 293, 360, 

 p. 295, 371-373, 376, p. 299, 404, p. 311, and 414, 415, p. 319, and pp. 286-292). 



Soft parts. — (1) A comprehensive term used to include all the organs or systems 

 except those directly concerned in the formation of the skeleton. 

 (2) The visceral mass. 



Spherodes. — See Ovoid bodies. 



Spicules. — Small, sharp-ended calcareous structures developed in the perisome, or 

 in the walls of the internal organs ; they may occur in the tentacles ; the spicules 

 occurring along the borders of the ambulacral grooves in many species are in 

 reality rudimentary side and covering plates. 



Spiny ciTri. — Cirri which have dorsal spines or processes developed on their outer 

 segments (see figs. 323, p. 277, 325, p. 279, 333, p. 283, 336-339, p. 285, 341-.343, 

 p. 287, 347-348, p. 289, and pp. 286-292). 



Spout-like processes. — The interradial processes of the rosette. 



Stalk. — See Column. 



Star stones. — See Pentacrini. 



Stem. — See Column. 



Stem syzygy. — ^An intercolumnar articulation occurring between the proximale and 

 the next ossicle below it, or between the reduplications of the proxmialc and the 

 ossicles next beneath (in the comatulid column between the centrodorsal and 

 the next following segment, and in the pentacrinite column between each nodal 

 and the following infranodal) which superficially i-escmbles a brachial syzygy, 

 more particularl}' a brachial syzygy of the type occurring in the pentacrinites. 

 It is in reality, however, a modification of a close suture and has no morpholog- 

 ical relationship to the brachial syzygy. 



Straight muscular articulation. — See Articulations Aa. 



Subamiulacral plates. — Plates developed beneath the ambulacral grooves. 



Suhcentral mouth. — A mouth is said to be subcentral when it is anterior to the center 

 of the ventral surface of the disk, and the two posterior ambulacra are more or 

 less longer than the other three. 



Submargincil anus. — An anus situated just within the outer margin of the anal area 

 (see figs. 18, p. 67, and 117, p. 183). 



Subradial cleft. — A deep, narrow cleft extending inward between the dorsal surface 

 of the radials and the apposed surface of the centrodorsal in the comatulids; it 

 usually reaches from the end of one basal ray to the end of the one adjacent ; 

 it always ends blindly (see figs. 194, p. 237, 203-205, p. 239, 208-216, p. 241, 

 and 531, pi. 2). 



The subradial cleft is the homologue of tlie interarticular pores of the 

 pentacrinites. 



Siihradials. — The plates situated immediately beneath the ratlials, between the 

 radials and the infrabasals. It is very rare to find subradiaLs developed all 

 aroimd the calyx, but in many t3'pes a single subradial occurs, beneath the 

 right posterior racUal, wMch has received the distinctive name of Eadianal. 



