1()2 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



conspicuous bund well up on the side of the ray, and are bounded below by a narrow 

 but fairly conspicuous intermarginal channel. 



The inferomarginal Bpinelets stand two (sporadically three) to a plate. They 

 arc subcylindrical and are both longer and stouter than the superomarginals. The 

 proximal spinelets may he nearly twice as long and 75 per cent thicker than supero- 

 marginals, and rather clavate in form. A series of actinal spinelets, similar to the 

 inferomarginals hut slightly larger, extends for two-thirds the length of the ray. A 

 few spinclots nl a second scries may be present at the base of the ray. The infero- 

 marginal and actinal spinelets together form three ventrolateral series separated from 

 the broad band of superomargina! spinelets by the intermarginal channel. 



Adambulacral plates diplacanthid for half or two-thirds the length of the fur- 

 row; the distals alternating diplacanthid and monacanthid; or the distal plates may 

 be irregularly diplacanthid. The furrow spinelet is, as usual, slenderer than the 

 adambulacral, which is subcylindrical and subclavate, about as long as the actinal 

 spinelets but considerably slenderer. Both become longer and decidedly slenderer 

 on the first dozen plates. The first five or six plates are monacanthid, and the first 

 three pairs are contiguous interradially. 



The oral plates have the usual arrangement of spinelets: Either one or two at 

 the actinostomial end, and one suboral. The longer of the slender apical spinelets 

 is as long as or a little longer than the median suture of the plates, and longer than 

 in alaskensis. 



Straight pedicellariae: There are a few small ovate or ovate-lanceolate, com- 

 pressed, bluntly pointed to obtuse pedicellariae in the supramarginal, intermarginal, 

 and actinal channels, and along the furrow face of the adambulacral plates, the 

 latter being quite small. They occur in clusters on the oral armature and mixed 

 with crossed pedicellariae on the furrow armature of the proximal half of the ray. 

 The lateral and actinal dermal pedicellariae are much slenderer than any of the 

 spines. The largest intermarginal measure 0.3 mm. (PI. 43, figs, 16, lc.) 



Abactinal crossed pedicellariae few and scattered, in circles around the spines. 

 They form rings or part rings on the superomarginal spinelets, and not very large 

 clusters on the outer side of the inferomarginal actinal, and adambulacral spines. 

 Abactinal pedicellariae measure 0.18 to 0.2 mm. (PI. 43, figs, la, la'.) 



Madreporic body circular, surrounded by one or two 1 cycles of granuliform 

 spinelets and situated at about the middle of r, or a trifle nearer the center of disk. 



Variations. — This species is typically small with short, rather stout, rays and a 

 close, uniform covering of granuliform spinelets. It is sexually mature at R 14 mm., 

 and the majority of the specimens have R less than 20 mm. The spine-counts in 

 these small examples are less than in the largest specimens, but the spines are more 

 uniform in size and distribution. Even in very small examples the actinal plates 

 extend for half the length of the ray. 



The superomarginal spinelets in small specimens form an arcuate vertical series 

 of three or four with an extra spine on the adoral, convex side of the arc. This is 

 essentially the arrangement in large specimens where extra spines appear on the 

 adoral side of the arc of usually five spinelets. 



Specimens from Unalaska, and a part of those from Adakh and Kyska are not 

 typical and approach, sometimes closely, what appear to be young L. camtschatica 



