A MONOGRAPH OF THE EXISTING CRINOIDS 177 



parting in the middle, and on the last 4 or 5 before the antepenultimate becoming a 

 pair of small erect median spines. The antepenultimate segment bears a single 

 median spine. The dorsal processes are rather high, reaching about one-quarter of 

 the width of the segments in height. The opposing spine is large and prominent, 

 triangular in lateral view, terminal, arising from the entire dorsal surface of the 

 penultimate segment, in height reaching one-half the width of that segment. The 

 terminal claw is slightly longer than the penultimate segment, stout, strongly curved 

 basally, but becoming straighter distally. The distal ventral edge of the cirrus 

 segments is slightly produced and very finely spinous. 



The distal ends of the radials are even with the rim of the centrodorsal. The 

 IBri are oblong, slightly over twice as broad as long, and not in contact basally. 

 The IBr2 (axillaries) are long, pentagonal, about as long as broad, with the lateral 

 edges nearly or quite as long as those of the IBr,. 



The 10 arms are about 90 mm. in length. The first 2 brachials are subequal, 

 slightly wedge-shaped. The first are about twice as broad as the median length, 

 interiorly united for the proximal half or two-thirds, the distal halves of the interior 

 sides diverging at a right angle. The second are somewhat longer. The first 

 syzygial pair (composed of brachials 34-4) is about as long as broad. The following 

 5 or 6 brachials are approximately oblong, those succeeding becoming triangular, as 

 long as broad, distally wedge-shaped and about as long as broad, and longer than 

 broad terminally. The IBr series and the brachials in the proximal fourth of the 

 arm have a faint narrow median keel. 



Pa is absent. Pi is from 7.5 mm. to 8 mm. long, very slender and tapering 

 evenly from the base to the tip, composed of 16 segments of which the first is broader 

 than long, the second is about as long as broad, and those following gradually increase 

 in length, after the seventh being 3 times as long as broad; the distal segments have 

 slightly spinous distal ends. Pj is 13 mm. long, slender (though stouter than P,) 

 especially distally, with 20 or 21 segments of which the first is not quite so long as broad, 

 the second is slightly longer than broad, and those following increase in length so that 

 the fourth and those succeeding are between 2 and 5 times as long as broad; the 

 fourth or fifth and following have the distal edge and the distal portion of the ven- 

 trolateral border prominently everted and spinous; the dorsal (outer) portion of the 

 outer edge of the segments is not produced. P3 is 7.5 mm. long, as slender as Pi but 

 stiffened, with 15 segments which resemble those of Pj. P4 is 6.5 mm. long with 16 

 segments, resembling P3 though shghtly more slender. Pj is 6 mm. long, slightly more 

 slender and less stiffened than P,, but with the same number of segments. The 

 following pinnules resemble Pj, soon slowly increasing in length, slenderness, and the 

 length of the component segments. 



The color in alcohol is deep violet, with the cirri a purplish flesh color. 



Locality. — Suez Bay; 18 meters; mud; Cyril Crossland [Chadwick, 1908; A. H. 

 Clark, 1909, 1911, 1912, 1918; Boulenger, 1913] (1 U. S. N. M., 27509). 



History. — This species was first noticed by Herbert Clifton Chadwick in 1908 who 

 recorded several specimens, under the name Antedon serripinna, from a muddy bot- 

 tom at a depth of 10 fathoms in Suez Bay, where they had been collected by Cyril 

 Crossland. Chadwick said that the cirri consist of 23 segments of which all, from 

 the fifth onward, have a transverse dorsal ridge. As in the specimens of this species 



