A MONOGRAPH OF THE EXISTING CRINOIDS 223 



short and those following gradually increase in length to the sixth which, with those 

 succeeding, is about as long as broad. The fourth and following segments have a 

 low transverse ridge extending entirely across their flattened dorsal surface which 

 in the earlier is subterminal in position, at about the eighth becoming median. This 

 ridge is finely spinous and appears as a very small dorsal spine in lateral view. The 

 opposing spine is delicate, median in position, standing out at right angles to the 

 dorsal surface of the penultimate segment, and not reaching quite half the width 

 of that segment in height. The terminal claw is rather longer than the penultimate 

 segment and is stout and strongly curved. The distal ends of the radials are even 

 with the rim of the centrodorsal. The IBr, are short, four or five tunes as broad as 

 their median length, with straight and free lateral edges. The IBr 2 (axillaries) are 

 triangular, about twice as broad as long, and rise to a rather prominent synarthrial 

 tubercle with the IBr,. The 10 slender arms are about 60 mm. long. The first 

 brachials are short, wedge-shaped, about twice as long exteriorly as interiorly, in- 

 wardly united for about the proximal half, the distal free edges diverging at rather 

 more than a right angle. The second brachials are similar in shape to the first but 

 slightly larger, rising in the proximal portion of the median line to a moderate synarth- 

 rial tubercle with the first. The first syzygial pair (composed of brachials 3+4) is 

 slightly longer inwardly than outwardly, and is about twice as broad as the longer 

 lateral length. The four following brachials are oblong, rather more than three times 

 as broad as long. The second syzygial pah- is wedge-shaped. The brachials following 

 are triangular, not so long as broad, later becoming wedge-shaped, broader than 

 long, and in the terminal portion of the arm as long as, or even longer than, broad. 

 After about the tenth the brachials have rather strongly produced and overlapping 

 finely serrate distal edges that give the dorsal surface of the arm a characteristically 

 rough appearance. This feature begins to die away in the outer half of the arm, 

 disappearing in the distal third. Syzygies occur between brachials 3+4 and 9 + 10 

 (rarely 10+11), from between brachials 14+15 to between brachials 17+18, and 

 distally at intervals of 5-8 (usually 5) muscular articulations. 



PI is about 4 mm. long, moderately slender, tapering evenly from the base to the 

 tip. It is composed of 16 segments of which the first 2 or 3 are not quite so long as 

 broad and the remainder are about as long as broad. In its outer half the pinnule 

 becomes styliform and then flattened. The last 10 segments have their distal dorsal 

 ends much produced so that the dorsal profile of the distal third, or rather more, of 

 the pinnule is very strongly serrate. P 2 is about 6 mm. long, much stouter than P,, 

 much the largest pinnule on the arm. It is composed of about 19 segments of which 

 the two first are not quite so long as broad and the remainder are approximately as 

 long as broad. After the third segment the pinnule gradually becomes sharply styli- 

 form, the distal dorsal end of the segments projecting in a rounded laterally flattened 

 tubercle which soon becomes very prominent. The base of this tubercle gradually 

 involves more and more of the dorsal side of the segments, in the last 10 or 12 arising 

 from the entire dorsal surface so that the terminal half of the pinnule, like the distal 

 third of PI, is deeply scalloped in profile. P 3 is about as large basally as PI, but it is 

 shorter, 3.5 mm. in length. It is composed of 12 segments of which the first three are 

 not quite so long as broad, the fourth is about as long as broad, the remainder become 

 gradually longer than broad, and in the terminal portion about twice as long as broad. 



