MONOGRAPH OF THE EXISTING CRINOIDS. 99 



suture and to the following columnal by a modified close suture or so-called 

 stem syzygy (which has no true morphological relationship with the superfici- 

 ally similar brachial syzygy) forming a proximale, which may be shortly 

 described as a columnal secondarily modified into an apical calyx plate. 



The proximale in its typical form is rare among the recent crinoids, but 

 appears as the centrodorsal in the comatulids, which, however, discard the 

 column between it and the next succeeding columnal. In the pentacrinites 

 the proximale and the larval column are indefinitely repeated throughout life. 

 In Bathycrinus and allied genera the proximale is many times reduplicated so 

 that a large number occur; but, instead of being distributed throughout the 

 column as in the pentacrinites, they are all restricted to the summit, forming a 

 cylinder or cone just beneath the crown. 



Pseudo-basal rays. The interradial ridges on the ventral surface of the centrodorsal 

 which, though an integral part of that structure, are indicated on its outer 

 surface by rounded tubercles resembling the ends of the basal rays (see fig. 

 250, p. 253, and pp. 330, 331). 



Pseudosyzygy. A non-muscular articulation closely resembling a syzygy, but of 

 entirely different origin, being developed from a synarthry; it occurs only in 

 places where a synarthry would be expected to be present. 



In certain species in which the synarthrial articulations become so close 

 that motion is rendered impossible, the synarthrial articular faces becomes 

 modified by the disintegration of the longitudinal ridge into several smaller 

 radiating ridges, while numerous additional radiating ridges, usually more or 

 less irregular, are developed so that the articulation, both externally and inter- 

 nally, comes to have all the appearance of a true syzygy (see figs. 37-40, 

 p. 75, and p. 113). 



R. 



Radial. Lying in the same line as the radii diverging from the radials. 



Radial areas. (1) The five areas in which lie the radials, or through the center of 

 which run the ambulacra. 



(2) On the centrodorsal, the five areas included between lines drawn from 

 the ends of the basal rays, or the interradial sutures, to the apex of the centro- 

 dorsal or to the center of the dorsal pole (see figs. 192, 194, 190, p. 237, 200, 

 203, 204, 207, p. 239, 208-216, p. 241, and pp. 230-232). 



Radial articular faces. The outer faces of the radials, wliich bear the straight muscu- 

 lar articulations by which the radials are articulated to the first post-radial 

 ossicles (see figs. 431, 432, p. 349, 439, 440, p. 351). 



Radial axillary. A term formerly used for the IBr or costal axillary. 



Radial canals. The tubular structures, more or less complete, within the calcareous 

 skeleton of the calyx wliich contain the radial prolongations of the water 

 vascular system (see p. 322). 



Radial circlet. The ring formed by the five radials. 



Radial cleft. See Subradial cleft. 



Radial commissure. See Commissure. 



