IIU 



BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



Figure 8. — Mastigometra micropoda A. 11. Clark, U.S.N.M., 35656: a, Part of postradial series; 

 b, cirrus; c and d, proximal parts of Pi and Pj. 



[Note by A.M.C] The specimen U.S.N.M. 35656 differs slightly from the one 

 described above in the proportions of the cirrus segments, most of which on the 

 peripheral cirri are longer than broad. The arms are notably constricted at the 

 syzygies. The breadth at the first is 1.5 mm. and the length from the IBri to the second 

 syzygj' is 9.0 mm. The longest cirrus has 16 segments and measures 11 mm., a shorter 

 detached one has 18 segments. The proximal pinnules are all broken. 



MASTIGOMETRA PACIFICA A. H. Clark 



Mastigometra pacifica A. H. Clark, Unstalked erinoids of the Siboga-Exped., 1918, p. 198 (in key; 

 range), p. 199 (description; Tahiti). 



Diagnostic features. — The cirri are about XXXV with 12-16 segments, of which 

 the distal are from a third to half again as long as broad; P, is 15 mm. long, with 30 

 segments; P2 is 10 mm. long, with 24 segments; P3 is 7 mm. long, with 13 to 15 segments. 



The arms are 105 mm. and the cirri from 12 to 14 mm. in length in the unique 

 holotj-pe. 



Description. — The centrodorsal is very flat, almost discoid al, 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 to 14 mm. long, 

 in general appearance strongly suggesting those of Antedon pefasus. The fu-st segment 

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

 fourth slightly longer than broad, fifth the longest, from a thu-d to half again as long 

 as the median diameter, the following have 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 tlie pro.ximal. Tlic opposing spine is minute; the terminal claw is nearly as long as 

 the penultimate segment, stout and strongly curved. The earlier cirrus segments iiave 



