199 

 2. Mastigometra pacifica nov. sp. 



The centrodorsal is very flat, almost discoidal, with a large flat dorsal pole 2 mm. in 

 diameter; the cirrus sockets are arranged in two and a partial third alternating marginal rows. 



The cirri are about XXXV, 12 — 16 (the longest usually 14 — 16), 12 mm. to 14 mm. 

 long, in general appearance strongly suggesting those of Antedon petasus ; the first segment is 

 very short, the second about twice as broad as long, the third nearly as long as broad, the 

 fourth slightly longer than broad, the fifth the longest, from one third to one half again as 

 long as the median diameter, the tollowing of about the same proportions; from the fourth or 

 fifth segment onward the cirrus in lateral view increases slowly in diameter so that the outer 

 portion, which is rather strongly recurved, is nearly twice as broad as the proximal; the 

 opposing spine is minute; the terminal claw is nearly as long as the penultimate segment, 

 stout and strongly curved. The earlier cirrus segments have a slight central constriction ; the 

 outer in lateral view have a quite straight dorsal, and a nearly straight ventral, profile. 



The distal border of the radials is even with the rim of the centrodorsal. 



The IBr x are very short, from five to six times as broad as long, with the distal and 

 proximal edges parallel and the lateral edges slightly convergent, making an angle of about 

 90 with those of the adjacent IBr p the perisomic area thus exposed being entirely covered by 

 a conspicuous group of perisomic interradials. 



The IBr., (axillaries) are triangular, half again as broad as long, with the anterior angle 

 somewhat produced. 



The brachials resemble those of the other species of the genus ; the distal edges are 

 slightly produced and finely spinous. 



Syzygies occur between the third and fourth brachials, again between the ninth and tenth 

 and fourteenth and fifteenth, and distally at intervals of three oblique muscular articulations. 



The arms are 105 mm. long, becoming extremely slender and attenuate distally. 



Pj is 15 mm. long, composed of 30 segments of which the first is broader than long, 

 the second half again as long as broad, and the third and following are twice as long as 

 broad, becoming longer in the distal half; from about the fifth onward the segments have 

 overlapping and prominently spinous distal ends. The pinnule is considerably stouter basally 

 than P., and the succeeding pinnules, but becomes exceedingly attenuated and flexible in the 

 distal half. 



P 3 is 10 mm. long with 24 segments, more slender than F Y with relatively longer 

 segments which have more prominently spinous distal ends. 



P., is 7 mm. long with 13 — 15 segments, tapering more gradually than P., and hence 

 appearing stouter, and without the long flagellate tip. 



P i apparently resembles P 3 , but is somewhat shorter. 



This species is described from two specimens from Tahiti, Society Islands, in the Zoolo- 

 gical Museum (Staatssammlung) at Munich; they were part of the lot including the specimens 

 upon which Euantedon tahitiensis is based. 



