172 A. Alcock — Account of the Deep Sea Collection. [No. 4, 



Family Astropectinidse. 



Dipsacaster, gen. nov. 



2. Dipsacaster, pentagonalis, n. sp. 



Differs from Dipsacaster sladeni (Ann. Mag. Nat. Hist., February, 

 1S93, p. 87, pi. V. figs 3 and 4) in the following particulars : — The disk 

 is relatively larger, and the rays, which are bluntly rounded at the tip, are 

 relatively shorter and broader — the whole form being thus more penta- 

 gonal ; the relative length of the rays to the radius of the the disk is 

 2*5 : 1 ; the paxillee are larger ; on the adambulacral plates the central 

 spine of the paxilliform group is a large distinct spine and not a mere 

 spinelet. Two specimens from the Andaman Sea, 112 fathoms. 



Family PentagonasteridsB. 



Calliaster, Gray. 



3. Calliaster mamillifer, n. sp., PI. VIII. figs. 3 and 4. 

 Kays 5 It = 25 to 3r. 



Abactinal area covered with sunken circular plates, each bounded 

 by a ring of discoid granules : the mid-radial plates of the disk bear 

 each a great globular mammillated spinelet, as do also, but on a smaller 

 scale, the dorso-central and basal inter-radial plates. 



The supero-marginal plates, which are six in number, excluding 

 the terminal, and come in partial contact across the distal third of the 

 rays, have the form of great globules, each surmounted centrally with 

 a nipple-like spinelet : those in the outer third of the ray sometimes 

 bear also one or two granules. 



The infero-marginal plates coincide not quite exactly with their 

 fellows of the supero-marginal series : they are long, broad and tumid, 

 and each bears near the suture line with that series, a row or a group 

 of large coarse truncated spinelets. 



The adambulacral plates have each a furrow series of four radiat- 

 ing spinelets, and actinally a single large coarse truncated spine and 

 rarely a few granules also. 



The actinal inter- radial areas are of some size, with large and 

 slightly tumid plates, raany of which have one, or very rarely two, large 

 coarse spinelets. 



All the marginal, adambulacral, and actinal plates have much the 

 same fringe of discoid granules or squames as the abactinal plates, only 

 it is not so regular. 



Anus subcentral. 



Madreporite small, circular, radially striated, situated about mid- 

 way between the margin and the centre. 



Colour in spirit, chalky yellow. This singularly beautiful species 

 was dredged in the Andaman Sea, between 270 and 245 fathoms. 



