A MONOGRAPH OF THE EXISTING CRINOIDS 155 



Description. The centrodorsal is almost columnar; according to the figure the 

 cirrus sockets are arranged in 10 columns with usually two to a column; the columns 

 seem to be in close apposition all around the centrodorsal. 



The cirri are about XXV, 30-35, according to the figure about 17 mm. long. The 

 three basal segments are almost saucer-shaped and those following become nearly or 

 quite twice as long as broad, soon becoming shorter again, about half again as broad as 

 long, and acquiring a marked dorsal keel which becomes reduced to a spine on the later 

 segments. 



The distal edge of the radials is fringed with blunt spines. The IBr t are short 

 with the proximal and distal borders fringed with blunt spines. The IBr 2 (axillaries) 

 are pentagonal with a curved base, overlapping the IBri laterally. The dorsal surface 

 of the elements of the IBr series is strongly convex and spinous, and their borders 

 are fringed with blunt spines. They are strongly flattened laterally against their 

 neighbors. 



The 10 arms are about 50 mm. long. The first brachials are rounded and short in 

 the median line, but with depressed lateral portions which meet one another by flattened 

 surfaces all around the calyx. The second brachials are more square and scarcely 

 project backward into the first. The margins of the lower brachials are fringed with 

 spines. The eighth and following brachials become quadrate and slightly overlapping, 

 with two or three large curved spines near the distal edge which become long and prom- 

 inent in the outer portions of the arms. 



Syzygies occur between brachials 3 + 4, again from between brachials 12+13 to 

 between brachials 15+16, and distally at intervals of 4 or more muscular articulations. 



PI is much larger than its immediate successors, with the three or four basal seg- 

 ments somewhat flattened on the outer side and the second-fifth with the inner edge 

 slightly keeled and folded upward. P is but little larger than P 2 , and the pinnules 

 following become gradually longer, with overlapping spinous segments. 



The disk is 6 mm. in diameter and is strongly plated. The brachial ambulacra 

 are irregularly plated. The pinnule ambulacra have large covering plates and ill 

 defined side plates. Sacculi are rare. 



The color hi alcohol is white with large dark brown patches on the calyx. 



Notes. The preceding description is adapted from the original description by 

 Carpenter with a few additions from his figures. Examination of the type specimen 

 in London showed that this is a well developed and comparatively large species. Gis- 

 len, who also examined the type specimen, wrote that the cirri are arranged in 10 col- 

 umns on the centrodorsal. The brachials have stout tubercles only, spines along the 

 border and in the middle of the synarthrial pairs, and no fine spinosity. He said it is 

 closely related to Stenometra, to which genus it ought, perhaps, to be referred. The 

 lesser number of arms than in Stenometra, he said, is- of less importance. 



Locality. Challenger station 147; between Marion Island and the Crozets (lat. 

 4616' S., long. 4827' E.); 2,925 meters; bottom temperature 1.2 C.; diatom ooze; 

 December 30, 1873 [P. H. Carpenter, 1888; Hartlaub, 1895; Shipley, 1901; A. H. 

 Clark, 1907, 1908, 1909, 1912, 1913, 1915, 1918; Koehler, 1924; Gislen, 1928] (1, B. M.). 



History. Antedon bispinosa was described and figured by Dr. P. H. Carpenter in 

 his report on the comatulids of the Challenger expedition published in 1888. In 1895 

 Dr. Clemens Hartlaub discussed its systematic position and bathymetrical relation- 



