218 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



practically capillary spinelets, slighth^ shorter to slightly longer 

 than the stout cylindrical convex pedicel. On the outer part of the 

 ray the pedicel is usuallj^ shorter than the spinelets. The madreporic 

 bod}^ is covered by about 20 very large paxillae, which stand on its 

 surface and about the edge. The spinelets are delicate and verj^ 

 numerous and when the crown is expanded it is 2 or even 3 times as 

 broad as that of an ordinary paxilla. The papulae are numerous and 

 distributed all over the abactinal area. 



The bases of the paxillae are very irregularly lobed and are 

 separated one-fourth to one-half their diameter. On the margin 

 of the area the plates are sometimes subquadrate in general form, 

 but elsewhere the plates are roundish with 5 or 6 short lobes or are 

 quite irregular. 



Marginal plates small, paxilliform, both series confined to the 

 ambitus; margin of ray thin, formed by the united bases of the 

 marginal paxillae. Superomarginal paxillae, 52 or 53, proximally 

 with the crown wider than long, distally with the crown cylindrical. 

 The spinelets are a little longer than the pedicel. Each superomar- 

 ginal stands directly above and close to the corresponding infero- 

 marginal which is half again as large, and consecutive pedicels are 

 separated by 1 or 2 times their diameter. The inferomarginal 

 I^axillae are wider than long at the crown and are about as high 

 proximally as the distance between the middle of one crown to the 

 middle of the next. These paxillae greatly resemble the marginal 

 paxillae of Solaster. The inferomarginals define the ambitus while 

 the superomarginals are dorsal in position. Terminal plate sub- 

 circular, with a shallow notch on the side toward paxillar area. It 

 is covered with short spinelets. 



Actinal interradial areas large, but narrower on ray than in R. 

 tizardi. A single series of plates reaches the end of ray. The plates 

 are arranged in very regular series, corresponding to the adam- 

 bulacral plates, and extending to the marginals but not correspond- 

 ing to them. The first 10 inferomarginals correspond to about 11 

 series of intermediate plates. The intermediate plates also form 

 regular longitudinal series or chevrons. The first chevron has paired 

 interradial plates behind the mouth plates, but most of the other 

 chevrons have an unpaired plate at the apex, interradially, though 

 sometimes out of place slightly. There are 10 or 11 of these chevrons, 

 the outermost very small. Halfway along the ray in R. tizardi 

 there are 8 or 9 plates in a transverse series ; in R. notdbilis only 5 ; 

 three-fourths the length of ray, in tizardi, 5 or G plates in a trans- 

 verse series, and in notahilis. only 2 or 3. Each plate bears on a low 

 eminence a cylindrical, paxilliform, penicillate group of 20 to 25 

 slender, sharp, closely coordinated spinelets, the peripheral about 



