lOfi Mr. A. Alcock on 



spinelcts and binall marginal pedicollariaj, and tlie crevices 

 between the ])lates giving exit to scattered distant papuUe. 



The rays witli a longitudinal mid-radial row of very large 

 tumid vertebra-i-]iaj)ed plates co-serial with the ])rimary radial, 

 each bearing a central globular or squatly conical spine; and 

 on each side of this mid-radial row seven (in tiic distal half 

 of the ray six) parallel rows of much smaller tumid octagonal 

 ])lates, the lowermost of which articulates with the adambu- 

 lacrals; these jdates, which also fall into transversely parallel 

 series, all bear distant capillary spinelets and small marginal 

 pedicellaria3, and all but those in the row immediately 

 adjoining the mid-radial row have a central long needle-like 

 spine, which is largest in the phites of the row adjoining the 

 adambulacrals. The pin-hole intervals between the angles of 

 neighbouring plates (except between the two lowermost rows 

 of plates) arc just large enough to give exit to a single small 

 papula. 



Adambulacral plates small, almost cylindrical ; each plate 

 bears on its actinal surface either three or four long sharp 

 spinelets in two transverse series, one of the spinelets which 

 adjoins the furrow often furnished with one or two small 

 pedieellari^e ; every alternate plate has a prominent intra- 

 ambulacral ridge, on which stands a row of two or three long 

 spinelets, of which the innermost bears a cluster of from six 

 to ten small pedicellarire and the outermost a single large 

 pedicellaria. The moutli-plates are armed with needle-like 

 spines similar to those of the other adambulacral plates. 



Tube-feet quadriserial, but the two middle feet of each row 

 reduced in size. 



Madreporiform plate very small, not half the size of the 

 basal plate, outside of which it lies almost hidden by over- 

 hanging spinelets. 



Gulf of Manaar, 597 fathoms, green mud; Laceadive 8ea, 

 705 fathoms, coarse coral shingle. 



This species is distinguished, (i.) by the high but flat- 

 topped disk, with its tumid stellate primary plates sparsely 

 covered with spinelcts; (ii.) by the strongly carinated rays, 

 pentagonal in section, with their median row of large 

 vertebra-sha])ed plates ; and (iii.) by the broad cylindrical 

 adambulacral plates with their two transverse series of actinal 

 spinelets. 



In a young specimen the disk, with its relatively enormous 

 tumid a[)ical plates, recalls the ap[)earauce of the Opliiuroid 

 Ojiliioniastus ; the relatively short rays (H = 8)-) end in a 

 large itiflated, helmet- like, two-horned plate^ and the tube- 

 feet are bisevial. 



