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



axillary without a syzygy, while the inner palmar series resembles the distichal one in 

 consisting of three joints, the axillary with a syzygy. This is shown very well in the 

 single example of Actinometra duplex, which has no very great number of arms 

 (PI. LXIV. fig. 3) ; and the fact that this arrangement is not merely an accidental one is 

 shown by its occurrence in three individuals of Actinometra belli (PL LXIV. fig. 1), and 

 in six of Actinometra nobilis (PI. LXV. fig. 1), both species having four post-radial 

 axillaries, and therefore a large number of arms. 



5. Actinometra belli, n. sp. (PI. LXIV. figs. 1, 2). 



Specific formula — a. 3. -A — \ 2.2. 



ab 



b- 



Centro-dorsal a moderately thick circular disk, hollowed in the centre, and bearing 

 about fifteen marginal cirri. These are fairly stout, of fifteen to twenty joints, a few of 

 which are rather longer than wide. 



The first radials are partly visible, and the second incompletely united; the rays 

 are quite separate from one another, but the intervening perisome is regularly plated 

 as far as the palmar axillary. The rays may divide five times, giving sixty-five 

 to seventy arms. 



Three distichals, the axillary with a syzygy ; palmar series two-jointed without a 

 syzygy on the outside of the ray, but three-jointed with a syzygy on the inside. 



The first and second post-palmar series, when present, are also two-jointed. The 

 anterior arms are long and slowly tapering, with one hundred and twenty to one hundred 

 and fifty overlapping joints, which are shortly triangular at the base, becoming quadrate 

 about the middle, and slightly elongated near the tip. The posterior arms are shorter and 

 taper more quickly, with only eighty to one hundred joints. A syzygy in the third 

 brachial ; the next about the tenth or twelfth, with others at intervals of three to six joints. 



The distichal pinnule is moderately stout and reaches 20 mm. in length ; the palmar 

 pinnule on the inside of the ray, and that of the second brachial are nearly as long ; 

 but that of the third brachial is only half their length and much more slender, while 

 the next pair are the smallest on the arm. The terminal pinnules are long and slender 

 on the anterior arms but shorter on the posterior ones. The basal segments of the 

 genital pinnules have sharp dorsal keels, which are less distinct in the first few pinnules 

 than in those immediately following. In the anterior arms they are lost after about the 

 fiftieth brachial, but are traceable to near the end of the posterior arms. The lowest 

 pinnules have a well-marked comb, which becomes gradually smaller and is lost about 

 the fifteenth brachial. 



Mouth interradial ; the disk bears a variable number of small granules, especially 

 round the ambulacra ; several of the hinder arms are ungrooved. 



