MONOGRAPH OF THE EXISTING CRINOIDS. 101 



Radicular cirri. Irregular branching cirrus-like structures developed on the ter- 

 minal columnals; they are primarily a development from the primitive terminal 

 stem plate (see figs. 5, p. 63, 540, 541, pi. 3). 



Ray. A radial, together with all the structures which it bears. 



Reductive regeneration. See Hi//* n< rut/mi Ai'. 



Regeneration. The rejuvenation of lost parts; Miuckert recognized four types of 

 arm regeneration among crinoids, as follows : 



(Al) Reproductive regeneration. The replacing of an arm lost by one 

 similar to it. 



(A2) Reductive regeneration. Regeneration resulting in a decrease in 

 the number of arms. 



(A3) Augmentative regeneration. The regeneration of an axillary and a 

 pair of arms in the place of a single arm lost. 



(A4) Multiplicative regeneration. The simultaneous regeneration of sev- 

 eral arms in the place of one lost. 



In the regeneration of the cirri ho recognized two types, as follows: 

 (Bl) Entire regeneration. In which a cirrus, lost at the articulation 

 between it and the centrodorsal, is replaced, and 



(B2) Partial regeneration. In which a cirrus broken oiF at some distance 

 from the base, regenerates the lost distal portion (see fig. 319, p. 275, and 

 p. 294). 



Reproductive regeneration. See Regeneration Al . 



Resorption. The dissolution and subsequent disappearance of any calcareous 

 structure. 



Right anterior arm. See Axis and Orientation. 



Right anterior interradial area. See Axis and Orientation. 



Right anterior ray. Sec Axis and Orientation. 



Right anterolateral ray. See Axis and Orientation 



Right lateral interradial area. See Axis and Orientation. 



Right posterior arm. See Axis and Orientation. 



Right posterior ray. See Axis and Orientation. 



Right posterolatcral ray. See Axis and Orientation. 



Rosette. A delicate calcareous plate with five radial and five interradial processes 

 situated within the circlet of radials just below the dorsal surface' of the radial 

 pentagon; it is formed by a curious process of transformation from the five 

 larval basals, and is not found except in the comatulids, among which it is 

 of almost universal occurrence so far as the recent forms are concerned, being 

 absent only in the genus Atclccrinus (see figs. 12, p. 65, 230, 231, p. 247, 301, 

 p. 264, 447-452, p. 353, 453-458, p. 355, 459-464, p. 357, 466-469, p. 359, 471- 

 476, p. 361, 477-482, p. 363, 483-48, p. 365, 490-495, p. 367, 49G-r.ni . p. 369, 

 503-508, p. 371, 509, 510, 512, 513, p. 373, 577, 57S, pi. 10, and 5X9-591, 

 pi. 14, and pp. 320-324). 



Row. Of cirrus sockets, a horizontal series, as contrasted with a column, or vertical 

 series (see figs. 149, p. 220, and 202, p. 23!), and pp. 226-228). 



