ECHI2TODERMATA. 161 



line of junction of the second and third. Distichals 2 ; palmars 2 : 

 in neither case is the axillary a syzygy, and in both cases there is a 

 slight conical protuberance where the two joints meet, and in both 

 cases also the more proximal of the two joints is in close lateral 

 contact with its fellow. First brachials a little wider along their 

 outer than their inner side ; along the latter they are again in close 

 contact with their fellow ; as the second brachial is also wider 

 without than within, there is a feebly-marked diamond-space 

 interval. The third brachial is nearly oblong, and, being syzygial, 

 has somewhat the appearance of a dice-box. For the next three 

 or four joints there is no wedge-shaped arrangement ; at first 

 feebly indicated, it rapidly becomes more marked ; further out it 

 diminishes, and the terminal joints are nearly oblong. As in 

 A. flaijellata (see Carpenter, Notes Leyd. Mus. iii. p. 183), the 

 earlier brachials are flattened on their outer side. 



The first syzygy is on the third brachial, the next about the 

 fifteenth, and there are then intervals of 9-10 joints between the 

 syzygies. 



The species is at once to be distinguished from A. flagellata by 

 the fact that the third is shorter than the first pinnule ; of the first 

 three the second is the longest. The first is on the second brachial, 

 and is but little shorter than the second ; the first three pinnules 

 all have broad basal and elongated distal joints, but though longer 

 than the next succeeding they are by no means remarkable in their 

 length. 



Colour : brownish flesh-coloured arms ; the peristome very much 

 darker ; the cirri much darker on their ventral than their dorsal 

 aspect. 



Disk incised, with a diameter of 7'5 millim. ; arms about 

 80 millim. long ; cirri 21 millim. long. 



Thursday Island. 



12. Antedon irregularis. (Plate XIII. figs. A, a-c.) 



Centrodorsal flattened, small ; cirri marginal, in two rows, about 

 25 in number (but there may be not more than 15), with 30-35 

 joints, the lowermost short, fourth to ninth longer than wide, then 

 again shortening ; no spine, except on the penultimate joint, and 

 that exceedingly small. 



First radials not (or barely) visible ; second wide, in contact, 

 with a median convex protuberance ; the third almost perfectly tri- 

 angular. 



Arms 11-22. Three joints in the first division, the axillaries 

 syzygies ; when there is a second division there are two joints, the 

 axillaries not syzygies. The earlier joints of the arm have a well- 

 rounded convex dorsal surface and are broader than long ; soon, 

 however, they become very markedly wedge-shaped and form a 

 prominent projection alternately on either side. Towards the end 

 of the arms these disappear. 



M 



