150 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



pore with the long axis at right angles to the dorso ventral axis of the animal is formed. 

 The midradial line rises into a broadly rounded elevation. The IBr 2 (axillaries) are 

 twice as broad as long or somewhat broader, triangular, with the lateral angles rather 

 broadly truncated. The proximal border is very slightly convex in the middle and is 

 slightly bowed downward over the truncated anterolateral angles of the IBri. The 

 distal edges are slightly everted and are armed with exceedingly fine spines, and the 

 proximal two-thirds of the median line is raised into a low and broadly rounded eleva- 

 tion. The outer portions of the proximal border are produced into a slightly everted 

 flange with a plain or sometimes broadly crenulate edge. 



The 10 slender arms are 180 mm. in length. The first brachials are wedge-shaped, 

 about four times as broad as the median length, and nearly twice as long exteriorly as 

 interiorly. The proximal border is slightly convex and is slightly everted. The inner 

 borders of the two first brachials borne by each axillary are in contact and are slightly 

 everted in the proximal half or two-thirds, the distal portion being slightly swollen and 

 sometimes armed with a spine or several spines. The distal border is very slightly 

 concave and the lateral portions are very slightly prominent. The second brachials are 

 about twice as large as the first brachials, and are trapezoidal. They are in contact 

 ulteriorly, and there is a narrow horizontally elongated water pore beneath their inner 

 ends. The first syzygial pair (composed of brachials 3 + 4) is approximately oblong, 

 half again as broad as long. The hypozygal is slightly longer interiorly than exteriorly, 

 and the epizygal has practically parallel sides. The next three or four brachials are 

 somewhat irregularly oblong, about three times as broad as long, with the dorsal surface 

 roughened and the proximal and distal edges slightly everted and armed with exceed- 

 ingly fine spines. The succeeding brachials are very obliquely wedge-shaped, almost 

 triangular, half again as broad as the greatest length, with the surface roughened and 

 the proximal and distal edges armed with a band of very fine spines, soon becoming 

 triangular and somewhat longer, at the middle of the arm becoming obliquely wedge- 

 shaped again, and nearly or quite as long as broad, and terminally longer than broad 

 with very oblique ends. After the proximal third of the arms the roughness of the 

 dorsal surface of the brachials becomes more pronounced, resolving itself into numerous 

 short spines with a broad base which are directed distally and tend to be arranged in 

 rows, and at the same time the production and spinosity of the distal edges of the 

 brachials increases. 



The first syzygy is between brachials 3 + 4, the second usually between brachials 

 15+16, sometimes between brachials 16+17, and once between brachials 17+18, and 

 the third is from between brachials 19 + 20 to between brachials 24 + 25. The distal 

 intersyzygial interval is from 5 to 12 (usually 7 or 8) muscular articulations. 



PI is 10 mm. long and is composed of 18 segments. It is stout basally and tapers 

 evenly and gradually to a delicate tip. The first segment is about half again as broad 

 as long, and those following gradually increase in length to the eighth, which is about 

 as long as broad or slightly broader than long. The following segments are similar, 

 becoming somewhat longer terminally. The outer side of the segments is sharply and 

 broadly flattened. The edge of the segments on the distal side of the flattened outer 

 surface is broadly rounded, somewhat elevated, and finely spinous; viewed from the 

 side it is seen to be somewhat convex. The proximal and distal angles of the outer 

 ends of the segments from the fourth or fifth onward extend beyond the bases of the 



