408 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xsxvi. 



Family ANTEDOXID.E. 



Genus IRIDOMETRA A. H. Clark. 



IRIDOMETRA EXQUISITA, new species. 



Centro-dorsal hemispherical, nearly covered ^yith cirrus sockets, a 

 very small convex polar area bare. 



Cirri XL-L, 14-15, exceedinglj^ slender and thread-like, 10 mm. 

 long; first joint short, second half again to twice as long as broad, the 

 following very greatly elongated, becoming shorter again on the ante- 

 penultimate, wdiicli is three times as long as broad, and the penulti- 

 mate, which is twice as long as broad ; the latter decreases slightly in 

 diameter distally, and may bear a minute terminal opposing spine, 

 though this is usually absent ; terminal claw about three-qtiarters the 

 length of the penultimate joint, slender, and slightly curved; the 

 articulations of the joints are greatly expanded, except in the terminal 

 five or six. 



Radials even with the edge of the centro-dorsal; I Br^ short, deeply 

 incised in the median line, in contact basally; I Br^ (axillary) rhom- 

 bic, twice as broad as long, the anterior angle produced. 



Ten arms, 40 mm. long; first brachial much longer outwardly than 

 inwardly, very deeply incised by the second brachial, barely in con- 

 tact basally over the anterior angle of the I Bro; third and fourth 

 brachials (syzygial pair) slightly longer interiorly than exteriorly, 

 about as broad as long exteriorly; next four brachials oblong, about 

 twice as broad as long, then becoming triangular, about as long as 

 broad, after the end of the proximal third becoming obliquely wedge- 

 shaped, rather longer than broad, and very gradually increasing in 

 length distally. Syzygies occur between the third and fourth brach- 

 ials, again between the ninth and tenth and fourteenth and fifteenth, 

 and distally at intervals of three oblique muscular articulations. 



Pj 6 nun. long, moderately stout basally, becoming slender distally, 

 somewhat stiffened, with thirteen joints; first joint twice as broad as 

 long, second half again as long as broad, third and following three 

 or three and one-half times as long as broad, becoming slightly shorter 

 terminally; P. similar, but more slender, 3 mm. long, with nine 

 joints, the first twice as broad as long, the second slightly longer than 

 broad, the third twice aa long as broad, the remainder greatly elon- 

 gated ; P., 2 mm. long, with eight joints, not tapering so rapidly as P. 

 (therefore appearing somewhat stouter), and bearing a small genital 

 gland in the distal portion ; the joints have slightly overlapping distal 

 ends; following pinnules similar; distal pinnules 6 mm. long, similar 

 to those in other species of the genus. 



Color (in spirits.) — AVhite, with blotches of brown on the arms 

 and pinnules; perisome brown. 



Ti/pe.—Cat No. 254T1, U.S.N.M., from Albatross station 5178; 

 north of Tablas Island ; 78 fathoms. 



