574 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



Siboga Exped., 1918, p. 108 (in key; range; synonymy; station 49a), p. 271 (listed). — Gisl£n, 

 KungL Fyslogr. Bfillsk. Bandl., now ser., vol. 45, No. 11, 1934, p. 25; Kungl. Fysiogr. Sallsk. 

 Lund Forh., vol. 7, No. 1, 1936, p. 4 (Macclesfield Bank); p. 6 (range). 



Diagnostic features. — The arms are 18-30 in number, 35-65 mm. long; the divi- 

 sion scries and arm bases have a narrow very dark median stripe; the cirri are XXI- 

 XX111, 29-36, 15-23 mm. long; the longest segments are about twice as long as broad, 

 and the outer segments are slightly broader than long, with long sharp dorsal spines. 



Description. — The centrodorsal is discoidal and usually rather small. 



The cirri are XXI-XXIII, 29-36, 15-23 mm. long. The first segment is very 

 short, the second is twice as broad as long, the third is slightly longer than broad, 

 and the fifth-seventh or -eighth are the longest, about twice as long as broad. The 

 segments following decrease hi length so that the outer, from the ninth or tenth onward, 

 are slightly broader than long. The tenth and following segments bear long sharp 

 dorsal spines, which are directed obliquely distally. 



The radials are short, about six times as broad as long, and are gently convex 

 proximally and correspondingly concave distally. The IBi'i are short, oblong, some- 

 what over four tunes as broad as long, and hi lateral apposition. The IBr 2 (axillaries) 

 are short, almost or quite triangular, two and one-half or three times as broad as long, 

 and in lateral apposition. The sides of the elements of the division series are from 

 slightly to rather broadly flattened. In some cases the radials and the portion of the 

 centrodorsal above the proximal row of cirrus sockets are evenly and thickly covered 

 with high small tubercles resembling those on the dorsal pole of the centrodorsal, this 

 tubercular modification of the dorsal surface of the segments extending distally hi the 

 interradial angles, occupying the lateral third of the IBri and IBr 2 and the IlBr 

 series, thence diminishing in width and disappearing on the second brachial ; the inner 

 borders of the IlBr series are similarly modified. In other cases the distal border of 

 the radials is finely beaded, and the dorsal surface carries a few well-spaced low tuber- 

 cles, while the lateral borders of the dorsal surface of the elements of the division 

 series are thickly beset with short papillae or short spines, this ornamentation along 

 the articulations between the axillaries and the ossicles preceding running inward 

 halfway to the median line in the form of a broad triangle. In still other cases the 

 lateral portions of the division series may be converted into a spongy-looking mass, 

 which causes their edges to appear denticulate. The IBr series have a low and nar- 

 row, but prominent, and more or less tubercular median keel or row of tubercles. 

 This is much less marked on, or altogether absent from, the IlBr series and first 

 two brachials, although it is sometimes traceable to the lowest of the triangular 

 brachials, or even to the arm tips. The elements of the IBr and IlBr series and the 

 oblong proximal brachials have prominently everted dentate proximal and distal ends; 

 as the brachials become wedge-shaped and triangular the everted dentate ends become 

 gradually lower, transforming into a rather prominent finely spinous overlap that 

 slowly dies away distally. When developed HIBr series are always external. 



The 18-30 (usually 24-30) arms are 30-65 mm. long. The proportions of the 

 brachials are the same as in M. subcarinata. 



P, is 4-5 mm. long, with 12-18 segments. The first four segments are broad, so 

 that the pinnule is moderately stout basally, but from the fifth segment onward it is 

 slender and flagellate. The first segment is from about os long as broad to slightly 



