REPORT ON THE ASTEROIDEA. 549 



7. Oribrella mfflata, n. sp. (PI. XCVI. figs. 5 and 6 ; PL XCVIII. figs. 1 and 2). 



Rays five. R = 80 mm. ; r = 12 mm. R<7 r. Breadth of a ray at the inflation near 

 the base, 13 to 14 mm. ; breadth of the same ray about midway between the disk and the 

 extremity, 7 mm. 



Rays elongate, rounded, and perfectly cylindrical, abruptly inflated near the base, the 

 inflation tapering off more gradually outwardly, the outer half of the ray being narrow 

 and attenuate. The tip is recurved in the specimen described. The disk is very small. 



The plates of the abactinal surface are small, and form a distinct but rather close net- 

 work. They are narrow and bevelled into an indistinct ridge, upon which are borne 

 extremely small, widely spaced, conical granules ; at intervals two or three are near 

 together, and form an incipient group. Upon the disk, where the granules are slightly 

 larger and the network closer, grouping is more apparent. These granules or incipient 

 spinelets are so small that they only produce a slight roughness to the touch when the 

 specimen is handled, and are invisible without the help of a magnifying-glass. There is 

 seldom more than one papula in each interspace. 



Along the lateral wall of the ray is a distinct narrow longitudinal line which traverses 

 the whole length ; this is composed of more compact and crowded groups of granules 

 borne on what are probably the representatives of a series of small narrow marginal plates. 

 A similar longitudinal line, in which the granules become more spiniform, may be traced 

 immediately external to the adambulacral plates, at least on the inner half of the ray. 

 The interspace between these two series gradually diminishes as it proceeds along the ray, 

 and may be roughly divided into two longitudinal areas, the lower of which is occu- 

 pied by rather large plates (in comparison with those hitherto mentioned) ; these are higher 

 than long, and bear more or less definite vertically disposed groups of papilliform granules, 

 separated by papula?. The upper part of the area bears small irregular groups, with 

 papulae interspersed. 



The armature of the adambulacral plates consists of about four pairs of spinelets (the 

 spinelets of each pair placed slightly obliquely), followed on the outer part of the plate by 

 one or two rows of two or three smaller spinelets, the whole forming a compact trans- 

 versely disposed group. The spinelets decrease in size as they recede from the furrow ; the 

 innermost pairs show some tendency to a subprismatic form, and have a rather thick 

 membranous sac. There is a single isolated smaller spinelet high up in the furrow. 



The madreporiform body is small, irregular, and indistinct. Its surface is marked 

 with few striations, which are not convoluted, and the intervening dissepiments are studded 

 with uniform, papilliform, rounded granules. 



The anal aperture, which is large and distinct, is distinctly excentric in position. 



Colour in alcohol, a warmish shade of light brown, but the greater part is bleached 

 into an ashy grey. 



Locality. — Station 170. North of the Kermadec Islands. July 14, 1874. Lat. 



