REPORT ON THE CRINOIDEA. 215 



extension into the purely littoral fauna is quite exceptional, for the members both of 

 the Basieurva-growp and of the Spinifera-groixp are almost entirely confined to the 

 continental and the abyssal regions. 



2. Antedon quinquecostata, n. sp. (PL III. figs. 6, a-d; PL XXXVIII. figs. 1-3). 

 Specific formula — A. 2. (2).—. 



Centro-dorsal a shortly pentagonal column with five interradial ridges veiy 

 prominent at their ventral ends, and separated by more or less alternating double rows 

 of cirrus-sockets, three or four in each row. About thirty-five cirri which may reach 

 45 mm. long, with eighty to ninety joints. Some of the lower joints are much longer 

 than wide, but the following ones become shorter and laterally compressed, with a sharp 

 dorsal keel, which passes into a prominent spine in the short middle and later joints. 



The angles of the first radials are just visible, being turned slightly outwards above 

 the interradial processes of the centro-dorsal ; the second are short and sharply convex, 

 rising to meet a strongly carinate backward process of the widely rhombic axillaries. 

 The rays may divide three times. Distichal and palmar series of two joints each, the 

 axillary not a syzygy. The two joints of each series, like the two outer radials, have 

 sharp median crests, which are continued out on to the arms. All these joints, and 

 especially those at the outer side of the ray, have straight lateral edges and flattened 

 sides. On some arms this character ceases at the second brachial, but in others it is 

 very visible on the third and even on the fourth. 



There are usually twenty arms (but one example has twenty-one), with a sharp 

 median keel, and composed of one hundred and twenty or more joints, which become 

 much compressed laterally so that the later ones overlap rather sharply. A syzygy in 

 the third, and then not till the twentieth or twenty-fifth brachial ; others at intervals of 

 four to eleven (usually five to seven) joints. 



The second brachial bears a moderately stout pinnule about 10 mm. long, and 

 consisting of some twelve or fifteen joints, most of which are longer than wide. The 

 first four or five are flattened on the outer side, where they meet the corresponding 

 pinnules of adjacent arms, and their inner edges are also slightly cut away. The 

 following pinnules are rather shorter, with more rounded joints, the two joints at the base 

 being wider than then- fellows on the lower part of the arm. Further out, however, this 

 is less marked, and the pinnules are somewhat carinate, but never specially long. 



Disk moderately plated, and the arms rather more so ; the pinnule ambulacra have 

 covering plates and partly differentiated side plates. Sacculi rare or absent altogether. 



Colour in spirit, — the skeleton yellowish-brown or whitish-brown, but the perisome 

 darker. 



