522 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



spinule moves nearer the furrow spinule, so that the formuUi is more 



ii + 1 

 properly — j — The aboral furrow spine is a little longer than the 



chord of the furrow margin and slightly longer than the adjacent 

 subambulacral spinule. The adoral subambulacral spine is usually 

 about two plates long, measured in the middle of the actinal sur- 

 face. The major spine is rather short, being 2 to 2^ plates in length 

 at base of ray, and 3 at the end of the costal region. The saccular 

 investment of the spines is conspicuous, often forming a wide flange 

 or sheet of tissue. Sometimes several major subambulacral spines are 

 joined together by their sacculi (by means of pedicellariae) so that the 

 spines appear to be merged in an actinolateral membrane. 



The mouth plates are longer than those of mifnica and the spine 

 which is directed across the mouth of the furrow reaches the other 

 side, being longer and stouter than in mimica. There is a short 

 actinostomial spinelet and a short aboral furrow spinelet. The slen- 

 der, acicular, suboral spine stands at the extreme outer end of the 

 plate and is usually invested in a common sacculus with its fellow, as 

 shown in the figure. 



Madreporic body on the margin, rather small, and surrounded by a 

 zone of plates free from spinelets. The articular surface of the am- 

 bulacral plates, where a ray has been broken from disk, is unusually 

 large, the height of the pair being Ih times the width, and about 1^ 

 times that of the same structure in B. mdmica (the disks are almost 

 exactly the same size). The figure will best show the exact form. 



Gonads, first adambulacral plates, and first marginal plates as in 

 generic diagnosis. 



Pedicellariae are best recognized from the figures. They are every- 

 ivhere smaller than in B. mimica. A disk pedicellaria is about 0.25 

 to 0.28 mm. long (0.45 mm. in ^nimica) and the proximal serrate por- 

 tion is longer in proportion to the length of the jaw. In the case of 

 the pedicellariae from the furrow spinelets, the difference is even 

 more noticeable (0.22 to 0.27 mm. in length, with more numerous 

 teeth in the serrate portion). Compare, also, figures of pedicellariae 

 from marginal mouth spines. 



Type.— C^t. No. 37033, 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. 



Distribution. — Known only from the type-locality. 



Rem,arks. — This species might easily be confused with B. mimica, 

 and superficially it greatly resembles also Stegnohinsinga placo- 

 dermit. The types of all three were taken at the same haul, and loose 

 arms were thoroughly mixed together. In the absence of disks, 

 B. anchista may be distinguished from B. mimica by the size and 



