520 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



bined plates at middle; an actinostomial spinelet just mesad to the 

 base of the inner furrow spine ; at outer end of plate a long acicular 

 suboral spine usually joined with its fellow in a common sheath 

 which is prolonged beyond the tip. All are heavily clad with pedi- 

 cellariae. 



Madreporic body very small, on rounded margin of ray. The 

 articular surface of the pair of ambulacrals of the disk, where a ray 

 has been broken off, is oblong elliptical in form, not oval as in B. 

 trachydisca^ and the height is equal to 1^ times combined width. 



The pedicellariae are distinctly larger than those of B. anchista^ 

 being 0.4 to 0.5 mm. long. In the case of the pedicellariae of the 

 furrow spinelets, ,the proximal serrate portion of the jaw has fewer 

 teeth than in anchista^ and is relatively smaller in proportion to the 

 length of the jaw (see figures). 



The papulae, gonads, first adambulacral and first marginal plates 

 as in generic description. 



Type.— C2,t. No. 37021, U.S.N.M. 



Type-locality. — Station 5648, Buton Strait, Celebes (lat. 5° 35' S.; 

 long. 122° 20' E,), 559 fathoms, green mud; bottom temperature 39.2° 

 F. 



DistHhution. — Known only from type-locality. 



Remarks. — This species differs from Biisinga insularum Alcock 

 and Wood-Mason in having 16 instead of 13 rays, isolated disk spine- 

 lets, not tufts, no intercostal ridges of pedicellariae, more numerous 

 costal ridges (13-17 in insularum)., a small madreporic body, much 

 shorter lateral spines (= 5.5 adambulacral plates as against 10 or 12 

 in iiisularutn) , somewhat shorter major subambulacral spine, longer 

 adoral minor subambulacral spine. If I understand the arrange- 

 ments of spines correctly, the formula for i7isularum^ would be 



i +1 



7^-—-^ -I- 1, which numerically is the same as the most characteristic 



formula of mimica. B. hengalensis has 14 rays, a small disk, with 

 the abactinal spinelets in tufts, 20 costae occupying basal ninth of 

 the ray, and intercostal bands of pedicellariae equally salient with 

 the ribs. The adambulacral formula is similar to that of mimica, 

 but the minor adoral and aboral subambulacral spines are not half 

 as long as their plate, from which it may be surmised that the plates 

 themselves are longer than iu mimica, and the aforesaid spines 

 shorter. They may also be true furrow spinelets in the sense I have 

 used the term, in which case the formula would be a bit unusual, 



-^-l-I. Of course the generic position of B. insularum and B. henga- 



letisis is not yet ascertained. 



This species superficially resembles Stegnohrisinga placoderma, 

 Avhich I have placed in a separate genus. The types of both spe- 

 cies were taken at the same haul. 



