118 Mr. A. Alcock on 



margin, one at each end of tlie plate, two spinelets as long as 

 the ])late; (iv.) deep within the furrow, on a distal ei)iphysis, 

 a spinelet which stretches across the furrow to overlap with 

 its fellow of the o})posite plate and separate tlie pairs of tube- 

 feet from one another. All these spines are hyaline, fluted, 

 and invested in membranous sacs which are closely felted 

 with ]iedicellariie. 



Actinostome large (25 millim. in diameter in the type 

 specimen). Mouth-plates of moderate size, each plate dis- 

 tinctly formed of two fused adambulacrals, of which they 

 bear the furrow and cross-furrow spinelets unchanged and the 

 actino-marginal spines but little modified. 



Madreporiform plate rather large, excavated centrally and 

 divided by a deep groove into two halves, with fine radial 

 striations, placed close to the margin of the disk. 



Colour in the fresh state bright cinnabar-red. 



Laceadive Sea, 1043 fathoms, green mud with foraniinifera. 



This species is characterized by its large disk Avith tough 

 membrane and coarse tufts of spinelets, and by the great 

 length and coarseness of its spinature. 



52. Brisinga andamanica^ Alcock and Wood-Mason. 

 Brisinga andamanica, Ann. & Mag. Nat, Hist., Dec. 1891, p. 439. 

 Kays 15. R = 27 r. 



Disk of moderate size (its diameter being 38 millim. in the 

 type specimen), with vertical edge ; rays very deciduous, but 

 not fragile, long, slender, a little depressed, but not inflated 

 in the ovarian region. 



Abaetinal surface of the disk much as in B. insularum, but 

 the membrane is not so tough, and the tufts of spinelets and 

 the tubercles on which they stand are not .so coarse. 



Abaetinal surface of the rays covered with a very delicate 

 transj)arent membrane, which in the proximal third of the 

 ray is strengthened by about forty-five rather distant cross 

 bands or half-bands of feebly developed spiny plates, in the 

 intervals between these bands, as throughout tlie whole ray at 

 regular intervals, occur very narrow felted bands of micro- 

 scopic pedicellariai. 



The vertebra-like adambulucral plates have the following 

 armature : — (i.) abactino-inarginally a spine about six times 

 as long as the plate ; (ii.) aeiino-marginally a spine about 

 four times as long as the plate ; (iii.) a single furrow spinelet, 

 placed at the adoral end, about equal in length to the plate; 

 (iv.) deep within the furrow, on a distal epiphysis, a cross- 



