234 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



rated. The first ossicles following each axillary are united interiorly for about the 

 proximal two-thirds, those following the IBr axillary then diverging at an acute angle, 

 those following the IIBr axillary remaining in apposition, though not united. 



Arms 16-20, about 150 mm. long, very slender. The first brachials are wedge- 

 shaped, about twice as broad as the exterior length. The second are similar in shape 

 and size. On arms arising from a IIBr axillary the first brachials are much larger, 

 being not greatly broader than the exterior length. The first syzygial pair (on arms 

 arising from the IIBr axillaries composed of brachials 2 + 3, and on those arising from 

 the IBr axillaries composed of brachials 3 + 4) is oblong, about half again as broad as 

 long, or slightly longer. The following 3 brachials (the following 1 or 2 on arms 

 arising from a IIBr axillary) are oblong, about twice as broad as long, those succeed- 

 ing becoming very obliquely wedge-shaped, about as long as broad, in the distal part 

 of the arm less obliquely wedge-shaped, almost oblong, about as long as broad, and 

 in the attenuated terminal portion longer than broad. After the first 2 or 3 the 

 brachials develop overlapping and finely spinous distal edges which become prominent 

 after the sixth or eighth, though their development is never very great; they are 

 plainly evident even in the attenuated terminal portion of the arm. 



Syzygies occur between brachials 3 + 4 (brachials 2 + 3 in arms arising from a 

 IIBr axillary), again between brachials 6 + 7 to 9 + 10, and distally at intervals of 4 

 muscular articulations. 



The mouth and anal tube are about equidistant from the center of the disk. The 

 mouth is radial. The disk is entirely covered with a pavement of very small plates, 

 with a few larger ones which rise above the general surface scattered about the inter- 

 ambulacral areas. In the lateral interbrachial regions of the disk the mass of small 

 plates tends to divide into two columns of large plates based upon a single plate in 

 the interradial angle. 



Pd is 12 mm. long, stout basally but tapering rather rapidly and slender and 

 Hagellate in the distal two-thirds. It is composed of nearly 40 segments, of which 

 the first is about twice as broad as long, the second is nearly as long as broad, the 

 third is of about the same proportions, and the following gradually increase in length, 

 becoming about as long as broad after the seventh and slightly longer than broad in 

 the terminal portion. The segments in the proximal third have very prominently 

 everted and spinous distal ends. The comb consists of 13 teeth, the terminal 2 or 3 

 more or less obsolete. The teeth are slightly longer than broad basally, about as 

 long as the width of the segment which bears them, rounded, well separated, and 

 beset with small marginal spines. Except for the first 2 or 3, all the teeth are double, 

 the segments bearing another similar, but smaller, tooth on the opposite side. Pi is 

 7 mm. Jong, much more slender than Pd though similar to it, and with a similar 

 comb. P3 is small, slender, and weak, 3 mm. long with about 15 segments, and bears 

 a more or less imperfect comb distally. P4 and the following pinnules resemble P3, 

 but are without combs. On arms arising directly from a IBr axillary. Pi resembles 

 Pd as described, P, resembles P,, etc. The distal pinnules are 9 mm. long, very 

 slender, with about 20 segments, of which the first is short, the second is half again 

 as long as broad, and those foUowmg become rapidly elongated and about three 

 times as long as broad. The segments all have very strongly overlapping and spinous 



