132 THE VOYAGE OF H.M.S. CHALLENGER. 



Pinnule-ambulacra well plated. 



Less than twenty smooth cirrus-joints; genital pinnules with broadly expanded 



joints and strong protecting plates, . ■ . . . .1. acaela, n. sp. 



Forty or more spiny cirrus-joints ; no enlargement of the genital pinnules ; first joint 



of lower pinnules much expanded, . . . . . .2. discoidea, n. sp. 



1. Antedon accela, n. sp. (PI. II. figs. 3, a-d; PI. XVI.; also Part I., pi. liv. 

 figs. 1-4 ; pi. lv. fig. 5). 



Specific formula — A. — . 



Centro-dorsal subcorneal or hemispherical, bearing twenty-five to thirty cirri. These 

 have fifteen to eighteen smooth joints, nearly all of which are longer than wide. 

 Terminal claw sharp, with but little trace of an opposing spine. 



First radials only visible in young specimens ; the second somewhat flattened, with a 

 convex proximal and concave distal border. Axillaries more convex, broadly pentagonal 

 or almost rhombic, with a wide distal angle, and sometimes projecting deeply backwards 

 into the second radials. The dorsal surfaces of both radials, with the two lowest brachials 

 and the hypozygals of the third, project beyond their faces and sides, especially the 

 latter, which fall away rapidly from the dorsal towards the ventral border. 



Ten arms. First brachials nearly oblong with rounded outer edges ; the second convex 

 and irregularly pentagonal. About one hundred smooth triangular joints, as long as or 

 longer than wide. Syzygies in the third and then about the eleventh or twelfth brachials, 

 with others at intervals of two to five, usually three or four joints. 



The first pair of pinnules have about thirty short joints, the lowest of which is a good 

 deal wider than the rest. From the fourth to the twenty -fifth brachials about three to 

 five of the pinnule-joints are greatly expanded laterally to enclose the genital glands, and 

 the first joint is much wider than its successors, especially in the lower pinnules. The 

 later pinnules have longer and more trihedral joints, the lowest of which are flatter. 



Disk rather incised and completely covered with irregular plates bearing short 

 and blunt rod-like spines. Brachial ambulacra and interarticular spaces well plated, and 

 the expanded parts of the genital pinnules are completely enclosed in an arched 

 ] lavement of flat plates, very regularly arranged and devoid of ambulacra. The ambulacra 

 of the later pinnules have very well-defined side plates, sometimes covering the sacculi 

 and sometimes notched for them. These are very abundant, except on the non-tentacu- 

 liferous genital pinnules. 



Colour in spirit, — young individuals straw-coloured ; the older ones a dense brownish- 

 grey, becoming a dark grey in the most mature. 



Disk 5 mm.; spread probably 20. mm. 



Locality.— Station 214, February 10, 1875 ; off the Meangis Islands; kit, 4° 33' N., 

 long. 127° 6' E.; 500fathoms; blue mud; bottom temperature, 41°-8 F. Several specimens. 



