388 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



to a broadly rounded distal border which reaches the distal border of the fourth 

 (epizygal) braclual, the eversion of this border being somewhat arched above it. The 

 lower border of this segment is convex; the upper, which bears the second segment, is 

 very deeply concave and only about two-thirds as long as the lower. The second 

 segment is much smaller than the first, but more than twice as broad as the third. 

 The lower border, by which it is attached to the first, is straight ; the distal border is 

 straight and parallel with the lower in the proximal two-thirds, but in the distal 

 third is expanded into a broad lobe which distally encircles the tliird segment and 

 reaches to the fourth. The third and following segments are very small, the third 

 being rather less than one-third as broad as the second. They taper very gradually 

 to the pinnule tip, and after the seventh become very slightly longer than broad. 



P2 is nearly 8 mm. long, longer and considerably stouter than Pi but of the same 

 general type, composed of 18 segments. The first segment is not so much enlarged 

 as the first segment of Pj. The second is about the same size as the second segment 

 of Pi. The third segment is about two-thirds as broad as the third segment of Pi. 

 The third and following segments gradually taper to the tip. The third segment is 

 rather more than half again as long as broad, the fifth is about as long as broad, and 

 the remainder are from half agaio to twice as long as broad. P3 differs from the pre- 

 ceding pinnules in being stiffened, spinelilce and prismatic with the first two segments 

 much less enlarged. It is 9 mm. long with 15 segments of wliich the third is about 

 two-thirds as broad as the second and the following gradually and regularly taper to 

 a sharp point. The third is about as long as broad, and the fifth and following are 

 about twice as long as broad with increasingly prominent and finely spinous distal 

 ends. The third and following segments have a prominent narrowly rounded carina- 

 tion. The distal pinnules are 10 mm. long with 20 segments of which the third and 

 following are about three times as long as broad, except the terminal 5 or 6, beyond 

 the distal end of the ambulacral groove, which are smaller and much shorter. 



Carpenter's description of the type specimen. — The centrodorsal is a thick disk 

 with the dorsal surface free; there are from 15 to 18 cirrus sockets in a single or partially 

 double marginal row. 



The cirri are XV-XVIII, 40-50, up to 27 mm. in length. A few of the earlier 

 segments are longer than broad and the following gradually develop a sharp dorsal 

 keel. 



The radials are short, except at the angles of the calyx where the ends of the basal 

 rays sometimes appear. 



The IBri are short, broad and oblong, and the IBrj (axillaries) are barely pentag- 

 onal. Both ossicles have large muscle plates, and their dorsal surfaces rise toward 

 the middle of their apposed edges. The IBr series are well separated. 



The 10 arms are about 80 mm. in length. The first brachials are almost oblong. 

 The second are bluntly triangular with a large lateral process bearing the pinnule 

 socket. The next few brachials each have a process of the same kind, but gradually 

 decreasing in size. After the tenth the brachials become triangular, as long as broad 

 and shghtly overlapping, and more quadrate distally. 



Syzygies occur between brachials 3+4, again between brachials 11 + 12 to 

 15 + 16, and distally at intervals of from 3 to 6, usually 4, muscular articulations. 



The first 2 pairs of pinnules have 20 or more short segments the first of which is 



