120 NATURAL HISTORY BULLETIN 



elongated, acute, divergent spinules. Between most of the radial 

 plates, over a large area, there are moderately large papular 

 pores, about six around etch plate. Smaller pores are scattered 

 over the center of the disk, but they are absent from small in- 

 terradial areas and from the distal part of the rays. 



The interactinal plates all bear dense groups of rather stout, 

 elongated, tapered, mostly acute or subacute spinules, essentially 

 like those of the lower marginal plates. 



The marginal plates of both series are densely covered with 

 small elongated, divergent spinules which overarch and partly 

 conceal the sutural furrows. The spinules on the upper plates 

 are slender and acute. Those on the lower plates, especially 

 those on the actinal side, are longer and much stouter, terete 

 and tapered, subacute or acute. 



The jaws are rather large, rhombic ; the two plates are separat- 

 ed by a rather wide sutural furrow covered with membrane; 

 they are covered with spines on the margin and actinal side, like 

 those of the adambulacral plates. The median, recurved epioral 

 spine is large, somewhat compressed; the distal part is hyaline 

 and very acute. 



The adambulacral plates are transversely oblong, rather nar- 

 rower than the adjacent interactinal plates. Each one, prox- 

 imally, bears two, or more often three, unequal spinules of the 

 furrow-series, but more distally they bear only two, nearly equal 

 ones. On the actinal face each plate bears about four or five 

 quite similar spines, which sometimes seem to stand, more or 

 less distinctly, in pairs. These spines, like those of the furrow- 

 series, are essentially like those of the interactinal plates, in size 

 and form. 



Eegularly 4-rayed and 6-rayed specimens have been taken. 



It is easily distinguished from our other species by the small 

 marginal plates and stout interactinal spinules. 



This species was taken by the U. S. Fish Commission at many 

 localities, from off Martha's Vineyard to Florida, in 43 to 480 

 fathoms and more. 



The Albatross also dredged another species in the West In- 

 dies, which is similar to 0. setosus Ver., if not the same. 



