322 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



laria similar to the abactinal, near the base of one of the lower spines^ 

 and sometimes 1 or 2 little granules; otherwise the surface of plate 

 is smooth, the margin being provided with a series of granules 

 similar to those of the abactinal plates. Terminal plate large, tu- 

 bercular, subglobose, acute proximally, showing scars of 4 to 6 

 terminal tubercles. 



Inferomarginals forming a rounded margin to ray, individually 

 tumid and decreasing regularly in size up to the last, the distal 

 not being enlarged. Four or 5 distal plates correspond to the en- 

 larged superomarginal. The first 5 or 6 plates are wider than long, 

 while the others, except the last 3 or 4, are longer than wide. The 

 proximal plates bear a central group of 6 to 8 spines, becoming re- 

 duced to 4 at the middle of ray, then 3, and finally 2 or 1 on the last 

 few plates. The spines are prominent, unequal, tapering, and sharp, 

 the longest being 3.5 to 4 mm. long. A peculiarity which they share 

 with the actinal intermediate and subambulacral spines, is in being 

 roughened by longitudinal rather irregular series of thorn}'' ridges 

 or protuberances, and the perfect spines end in several verj'- short 

 thorns or points. The protuberances on the sides of the spines vary 

 considerably in form, being sometimes carinate, interrupted, ridges, 

 and again formed like blunt rose thorns. The dist almost spines are 

 nearly or quite smooth. Most of the plates bear 1 or 2 pedicellariae, 

 similar to those of the superomarginals, and are bordered by a single 

 series of small oblong semi-immersed granules similar to those of 

 the superomarginals. 



Actinal intermediate plates in 3 chevrons, with an odd plate inter- 

 radially adjacent to margin. The plates adjacent to adambulacrals 

 are 6-sided or sometimes distally 4-sided and reach as far as the 

 middle of the fourth inferomarginal. Nearly all the plates bear a 

 central, tapering, sharp, thorny spine about as long as the infero- 

 marginal spines, and at its base a small, blunt, spatulate pedicellaria 

 with 2 swollen jaws, usually constricted at the middle, 1.5 to 2 times 

 as high as wide. The plates are bordered by slightly convex, or 

 flattish granules immersed in membrane. 



Adambulacral plates slightly convex, wider than long proximally, 

 becoming as Avide as long in middle of ray, and again wider than 

 long at the tip. Furrow margin slightly convex, bearing a close 

 comb of proximally 12 or 13 spinelets, increasing gradually to 16 or 

 17 at the middle of ray. The small plates near the tip have a de- 

 creasing number, the last 10 plates diminishing from 10 or 11 to 4 

 or 5 spinelets. The spinelets are slender, compressed, blunt, close 

 together, webbed for nearly half their length, and form a straight 

 or slightly convex-edged comb, abruptly rounded at the corners, 

 where 2 or 3 lateral spinelets, sometimes with the flat side to furrow,, 

 become very rapidly shorter, so that the first and last spinelet is 



