MONOGRAPH OF THE EXISTING CBINOIDS. 



101 



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

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

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



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



Reductive regeneration. — See Regeneration A2. 



Regeneration.— The rejuvenation of lost parts; Minckcrt recognized four ty]>es of 

 arm regeneration among crmoids, as follows: 



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



similar to it. . 



(A2) Reductive regeneration.— Regeneration resulting m a decrease m 



the number of arms. 



(A3) Augmentative regeneration.— The regeneration of an axiUar}- and a 



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



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

 eral arms in the place of one lost. 



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



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

 between it and the centrodorsal, is replaced, and 



(B'^) Partial regeneration.— In which a cirrus broken oiT at some ihstance 

 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.— See 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 posterolateral mi/.— See Axis and Orientation. 



Rosette -A delicate calcareous plate with five radial and five mterradial processes 

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

 nentacron- it is formo.l by a curious process of transformation from the iive 

 arvafbasals, and is not found except m the comatulids, among wluch it is 

 of ahnost universal occurrence so far as the recent forms are concenied being 

 absent only m the genus Atelecnnus (see figs. 12, p. 6;., 230, 231, P-2-t' ,'>^'l' 

 p 2T4 44-452, p. 353, 453-458, p. 355, 459-464, p. 357, 466-469, p. 359, 471- 

 $76 n 361 477-?82, p 363, 483-489, p. 365, 490-495, p. 367, 496-501, p. 360, 

 5oL';8, p 371, 509' 510, '512, 513, p. 373, 577, 578, pi. 10, and 589-591, 



t)l 14, and pp. 320-324). 

 Rou^^Of Cirrus sockets, a horizontal series, as contrasted .nth a cohunn, or v.-rtical 

 series (see figs. 149, p. 220, and 202, p. 239, and pp. 226-228). 



