214 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Spinelete fewer, there being only 1 or 2 to a plate bej'ond the papular 

 area, and on papular areas (including center of disk where papulae 

 are absent) there are 1, 2, or 3 spinelets to a plate. On the scattered 

 plates which have small spines there are 1 to 3 small spinelets in 

 addition. In B. polyctenms^ of the same size, the plates of ray have 

 upward of 5 spinelets, and on the disk 2 to 5. On the disk and as 

 far along ray as papulae extend are rather numerous prominent 

 subcircular pectinate pedicellariae composed of 2 or 3 combs having 

 each 3 to 5 acute spinelets. 



Papulae extending to distal margin of third superomarginal plate 

 (second in cotype), a little farther than in a comparable specimen 

 of 'polyctenius. 



Superomarginal plates in form and posture closely resembling those 

 of B. polyctenius^ but the accessory spines lacking, there being only 

 a small spinule on the first 2 or 3 plates. The odd plate bears a rela- 

 tively immense sharp spine (14 to 17 mm. long), as long or longer 

 than diameter of disk, and the most characteristic feature of this 

 species. This spine is about 7 mm. long in a comparable specimen 

 of B. polyctenius. 



The inferomarginals bear 2 spines, the lower one-half to three- 

 fourths the length of the upper, similar to those of B. polyctenius. 

 The plates of outer third of ray are very slender and bear, as a rule, 

 onl}^ 1 spine. Between the plates of proximal half of ray is a pecti- 

 nate pedicellaria, but these may be absent from a number of plates, 

 their occurrence being subject to variation. 



Actinal interradial areas small, bearing each 2 large pectinate 

 pedicellariae (one interradius has 2.5 pedicellariae). 



Furrow spines 7 or 8, slender, bluntly pointed, the successive 

 combs spaced a little less than their base line. (In B. polyctenius a 

 comparable specimen has 9 to 11 spines, the combs spaced only one- 

 half the length of their base line.) Subambulacral spines 2, the outer 

 slightly the shorter, with a third quite small spinule usually present 

 adorad of the outer spine. Nineteen to 22 plates correspond to first 

 10 inferomarginals, omitting the odd plate. 



Oi-al spines G; suboral, 3, in a series along middle of plate. The 

 armature resembles that of B. polyctenius^ which ma}^ have a feAv 

 more spines, but the number of spines is variable. 



Madreporic body slightW spaced from the odd superomarginal, 

 convex, with radiating striae. 



Type.— Cat. Xo. 32631. U.S.N. M. 



Type-locality.— Stixt'wn 560)8, Macassar Strait (lat. 2° 28' 15" S.; 

 long. 118° 49' E.), 901 fathoms, gray mud. bottom temperature 38.2° 

 F. ; 2 specimens. 



Distribution. — Known only from the type-locality. 



