552 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



These five plates, if they are in reality as they appear five separate units, 

 probably have resulted from the unequal and exclusively interradial growth of 

 the outer portions of the columnal immediately following the centrodorsal. 



The columnal following that beneath the five plates just described is dis- 

 coidal, about two-thirds of its diameter and about two-thirds of its length, with 

 the sides slightly converging distally. The next is similar and of the same length, 

 but very slightly less in diameter and with parallel sides. The following is about 

 twice as long, and the next, to which it appears to be united by a bourgeticrinoid 

 articulation instead of by more or less uniformly distributed ligaments, longer 

 still. From this point onward the length of the cohimnals slowly increases, the 

 twenty-fifth and following being between three and three and one-half times as 

 long as broad. In the outer half of the column as preserved the ends of the 

 segments become rather prominent and the lateral profile evenly concave. 



There are 15 cirri present: the longest of these — those of the middle inter- 

 radial row, reach to the base of the seventh brachial and are composed of 14 

 or 15 segments, of which the first is twice as broad as long, the second is slightly 

 broader than long, the third is nearly twice as long as broad, the next two are 

 slightly over twice as long as broad, and the remainder are about half again 

 as long as broad as the base. In the second-fifth segments the outer portion 

 increases slightly in diameter in lateral view, and the distal dorsal border is 

 armed with numerous prominent spines. Beyond this point the segments become 

 more compressed laterally, and the increase in diameter in lateral view is uniform 

 from the base to the distal end, which dorsally is armed with prominent spines. 

 On the antepenultimate segment there is a fine serrate middorsal carination, and 

 on the last a small sharp terminal opposing spine. The terminal claw is slender, 

 moderately curved, and slightly longer than the segment which bears it. 



The radial cirri about the tip of the centrodorsal, alternating with the five 

 plates, which are the oldest, reach to the base of the third brachial and consist 

 of 12 segments. They resemble those just described. 



The interradial peripheral cirri, which are the youngest, are as yet rudi- 

 mentary, and do not quite reach the distal border of the IBr,. 



The basals form a complete, though low, ring about the calyx. Beneath the 

 convex proximal border of the radial radials the lateral portions of the basals are 

 very narrow; interradially, where their distal angles are broadly truncated by the 

 proximal borders of the interradial radials, they are about twice as high. 



The radial radials have almost attained the perfected form, though the 

 articular face is still rather narrow, falling considerably short of reaching the 

 lateral borders. Their distal edges bear numerous rather short conical spines 

 arranged in a narrow band. 



The interradial radials, of which the distal ends are at the same height as 

 those of the radial radials, are only about half as broad as the latter, and reach 

 proximally for only about two-thirds of the distance, where they abut against 

 the truncated distal angles of the basals. 



The radial arms are very long and well developed. All of them have lost 

 the tips. The longest consists of 22 brachials; when perfect it probably had 



