702 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



borders of the shorter outer segments usually project ventrally, considerably beyond 

 the bases of the succeeding segments, and may be armed with a minute but sharp 

 forward projecting spine. The smaller cirri nearer the dorsal pole resemble the longer 

 peripheral cirri, but the decrease in the length of the segments distally is much more 

 rapid so that there are more of the short outer segments, and these are also shorter. 

 The opposing spine is terminal, usually rising from the whole dorsal surface of the 

 penultimate segment, its distal edge continuing in the same line as the distal border 

 of that segment than which its height is slightly to considerably less. The terminal 

 claw is longer than the penultimate segment, slender, evenly tapering, and evenly 

 curved. 



The distal edge of the radials is even with the proximal border of the centrodorsal, 

 or appears just beyond it. The IBri are very short, about four times as broad as their 

 slightly convergent lateral borders which are not quite or only just in contact basally 

 and diverge at an angle of 60 or even more, and very deeply incised in the median 

 line by a posterior projection from the IBr 3 (axillaries) which are rhombic, usually 

 about as long as broad, with all the sides concave, and rise to a slight rounded tubercle 

 on the articulation with the IBrj. 



The 10 slender arms are from 75 to 110 mm. (most commonly between 85 and 100 

 mm.) in length. The first brachials are very short, just meeting basally over the 

 anterior angle of the IBr 2 , longer outwardly than inwardly, very deeply incised in the 

 median line by a posterior projection from the second brachial, which last is rather 

 large and irregularly quadrate. The third and fourth brachials together form a syzygial 

 pair which is slightly longer interiorly than exteriorly, as broad as its interior length. 

 The following four brachials are wedge-shaped, about twice as broad as their median 

 lengths, with the anterior and posterior borders very concave. The second syzygial 

 pair, formed of the ninth and tenth brachials, is similar, but slightly longer. The 

 following brachials are very obliquely wedge-shaped, almost triangular, about as 

 long as broad, distally gradually becoming more elongate, and terminally long with 

 swollen articulations. 



Syzygies occur between brachials 3+4, 9+10, 14+15, and distally at intervals 

 of 3 muscular articulations, with rare exceptions. 



In a specimen with arms about 80 mm. long, P, is 15.5+ mm, long, with 28 + 

 (probably 30), segments, excessively slender and threadlike, though stiff; the first 

 three segments are broader than long, the fourth is slightly longer than broad, and 

 the following rapidly become exceedingly long and slender with everted and spinous 

 ends. P 2 is 6 mm. long, with 12 segments, stouter basally than PI, and tapering 

 evenly to the extremely delicate tip; the first segment is short, the next two are about 

 as long as broad, and the following rapidly become elongated. P 3 is 6.5 mm. long 

 with 14 segments, resembling P 2 . PI is 7 mm. long with 14 segments, tapering more 

 slowly than P 3 and with a more or less developed genital gland. The distal pinnules 

 are 12 mm. long with 20 segments, very slender; the first segment is trapezoidal, 

 broader than long, the second is trapezoidal with the base against the base of the preced- 

 ing, tapering distally, about as long as broad basally, and the following segments are 

 greatly elongated with rather abruptly everted and finely spinous distal ends. 



In a specimen from off Martha's Vineyard, Gislen found P a to be 15 mm. long with 

 26 segments, and P b to be 4 mm. long with 10 segments. 



