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



1. Antedon angusticolyx, n. sp. (PI. II. figs. 4, a-d ; PL L. figs. 1, 2 woodcut on 

 p. 246, fig. 5, B ; also Part I. pi. liv. fig. 5 ; pi. lv. fig. 6). 



Specific formula — A. 3. "o.y. 



Centro-dorsal a truncated hemisphere, marked by indistinct interradial ridges which 

 are produced upwards into rather prominent processes between the radials. Twenty to 

 twenty-five cirri, of eighteen to twenty-three smooth joints, most of which are slightly 

 longer than wide ; the penultimate without an opposing spine. 



First radials entirely concealed ; the second quite short, especially in the middle line, 

 barely in contact above the angles of the centro-dorsal. They are deeply incised by the 

 tubercular backward processes of the axillaries, which sometimes almost reach the centro- 

 dorsal. Three distichals, the junction of the first two somewhat tubercular, and the 

 axillary a syzygy, in close contact with its fellow on the next ray. The outer radials 

 and the three distichal joints have sharp straight edges, and both sides flattened, and the 

 first two or three brachials may show the same characters, but to a less extent. 



Fourteen to twenty arms, of over one hundred joints, of which the lowest are nearly 

 oblong, their successors triangular, and wider than long, gradually becoming longer and 

 more quadrate. 



The first syzygy is in the third brachial when the primary arms do not divide, and 

 the next between the eleventh and fifteenth. When distichals are present the first two 

 brachials are usually united by syzygy, and the next syzygial joint is from the 

 seventh to the twenty-fifth brachial, usually about the twelfth or fourteenth. After 

 this an interval of four to twelve, generally six or seven joints, between successive 

 syzygia. 



The distichal pinnule is about 9 mm. long, and consists of some thirty short, carinate 

 joints, the lowest of which, though thick, are not specially wide. The next two or three 

 pinnules are of about the same length, with relatively longer terminal joints, and the 

 lower ones somewhat Matter. The following pinnules are a little shorter, with the first 

 two joints smaller than in the proximal pinnules ; but the third joint and from two to 

 four of its successors are broad and flattened, with the outer edges much produced towards 

 the ventral side. Traces of this expansion may be visible as far as the twenty-fifth 

 brachial, after which the joints become elongated and the pinnules more slender. 



The disk is much incised and completely plated, as are also the brachial ambulacra 

 and the interarticular spaces. The genital glands are covered by closely set plates in 

 which sacculi are embedded. These are small and inconspicuous on the pinnule- 

 ambulacra, which have well-defined side plates. 



Colour in spirit, — light whitish-brown; 



Disk 7 mm.; spread 15 cm. 



