482 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



cover the first 1 or 2 plates of the other series, as far up as the lower 

 border of the siiperomarginals. These three lower series (or 2 in 

 smaller examples) have a central flattened, sharp spine on many of 

 the plates, often arranged so that alternate transverse rows lack one, 

 or all of the central spines, which are therefore in spaced, often in- 

 complete transverse combs. On the outer third of the ray the carinal 

 and marginal plates (the latter being the only naked plates reaching 

 end of ray) are armed with an appressed, tapering, sharp spine about 

 as long as its plate. There is no trace of this on the young specimen,, 

 although present on an adult from the same station (5607). Very 

 small pedicellariae occur sparingly on the 3 lower rows of armed 

 plates, and distally on the abactinal naked plates. 



Prominent adambulacral plates with a transverse series of 4 or 

 5 spines, the innermost rather deep in the furrow and directed hori- 

 zontally between 2 tube feet; the next 2 longer, erect, flattened, 

 acute, slightly curved, and tapering from a stout base; the outer 1 

 or 2 shorter, flattened, and more or less leaflike. The innermost 

 2 spines (or the second only) bear each a large pedicellaria, fre- 

 quently as long or even longer than the spines, and sometimes accom- 

 panied by one to several small pedicellariae, especially at the base of 

 the ray. One jaw of the pedicellaria is spatulate, larger, and more 

 curved than the other, resembling a miniature duck's beak; or the 

 jaws are nearly equal and the distal half of the pedicellaria is curved, 

 something like a miniature ibis's beak. Along the adoral, transverse 

 margin are usually two squamif orm" spinelets. In the specimen with 

 granular disk plates from station 5602 there are sometimes 3 spinelets 

 in this series, and the one nearest furrow is tapered and bears one 

 small pedicellaria (or at the base of the furrow, several). Nonpromi- 

 nent plates with usually 5 spines, in 2 transverse series (3 spines 

 in the adoral). Usually the 2 aboral spines are flattened and 

 squamiform, and the adoral tapered but often the outermost of the 

 adoral spines is also squamiform. The innermost of that series is 

 short, tapered, and stands a little out of line on the furrow margin 

 of plate. It usually (but not always) bears a pedicellaria longer than 

 the spine, solitary or accompanied by 1 to 3 very small ones at its base. 



In the young specimen from station 5202 the plates are subequal 

 and armed with a transverse series of 4 or 5 spines, the inner- 

 most slender, tapering, and sharp, the others increasing in thickness 

 and becoming more flattened toward the outer end of the plate. 

 Adorad to these there is often but not always 1 short spinelet, rarely 2. 

 Sladen mentions, in the description of the immature t3^pe, only the 

 series of 5 spines, but his figure (1889, pi. 68, fig. 4) shows the small 

 adoral spinelet. 



Madreporic body small (1.5-2.5 mm.), and surrounded by gran- 

 ules or very short, stubby spinelets. Tube feet in 4 crowded series 



