PART 5 A MONOGRAPH OF THE EXISTIiSfG CRINOIDS 33 



next two bracliials are about twice as broad as the median length and have shghtly 

 obhque ends. The brachials following, which alternate with sj'z^ygial pairs, are similar, 

 but the ends become somewhat more obhque. In the outer half of the arm the brachials 

 are about half again as broad as long. 



Syzygies occur between brachials 3+4, 7 + 8, and 12+13, thence at intervals of 

 two muscular articulations. 



There are 17 or 18 pinnules on each side of the arm. 



Pi is 7.5 mm. long, with 14 segments, and tapers evenly from a moderately stout 

 base to a slender but not delicate tip. It is moderately flexible. The fu-st segment is 

 about as broad as long, with the proximal border rounded. The second is about a 

 thh-d again as long as broad. The thu'd is somewhat over twice as long as broad. 

 The fom-th and following are about three times as long as broad. The pinnule is per- 

 fectly smooth, the segments joining evenly end to end without any production of the 

 distal ends. From the third onward the segments on the middle of the outer side bear 

 a narrow roughened line marking the crest of a sHght compression. 



Pa is 4.2 mm. long, with 10 segments, resembhng P, but correspondingly smaller 

 and more slender. 



P2 is 3.0 mm. long, with 11 segments, of which the first is about as long as broad 

 and ^vith the proximal border well rounded, the second is about as long as broad, the 

 third is about half again as long as broad, the fourth is a little longer, but the fifth is 

 shorter and only shghtly longer than broad. The following segments are all slightly 

 longer than broad, though shorter than the fifth. The pinnule is rather stout basally 

 and tapers evenly and regularly to a rather broad and stout distal portion. The 

 thu'd to fifth segments support a large ovoid gonad and marsupium, of which the side 

 toward the base is thick and tough and the side toward the pinnule tip is thin and 

 dehcate. The third and following segments have a thin but prominent carinate ridge 

 on the middle of the outer side. 



P3 is 3.3 mm. long with 11 segments and resembles P2. 



P4 is 3.5 mm. long and resembles P3. 



The following pinnules to Pg are similar, the gonad then gradually diminishing in 

 size and disappearing after Ph. 



The distal pinnules are 3.5 mm. long with 12 to 14 segments. The first segment 

 is about twice as broad as long, the second is about as long as the pro.xhrial width, 

 broader proximally than distaUy and with shghtly concave sides, and the remainder 

 are about half again as long as broad. The terminal segment is enlarged and has the 

 broad dorsal surface armed with 12 to 15 stout recurved spines. The segment preced- 

 ing is somewhat less enlarged and is armed dorsally ^vith smaller spines or tubercles. 

 The segment before this is often shghtly enlarged. The distal pinnules are obscurely 

 and broadly carinate, usually narrowly and sharply carinate on a few of the segments, 

 or at least part of them. The proximal end of the last segment and the distal end of 

 that preceding are very sharply oblique, so that the fibers connecting them are very 

 long, allowing for an unusual amount of motion, and the two preceding articulations 

 are nearly as flexible. 



The disk appears naked on superficial examination, but is in reality completely 

 covered vdth a continuous pavement of smaU and very dehcate plates that become 

 more regular and more conspicuous along the ambulacra. On the long anal tube there 



