578 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



arranged in 2 or 3 alternating rows instead of in a continuation of the more proximal 

 columns, and the sockets in these rows usually have slightly more prominent rims 

 tlian the others. In the j'oungest specimens the cirri are in 2 or 3 alternating rows; 

 later the more proximal appear in 3 columns, and when nearly full size has been reached 

 in 4 cokunns, the median colunm becoming 2. The 4 columns appear when the arm 

 length is about 110 mm. and the cirri are about 50 mm. long, with about 36 segn^ents. 



The cirri are numerous, I^-LXXVIII, the peripheral 50 to 75 mm. long (usually 

 between 50 and 60 mm.), with 32 to 50 (usually 35 to 45) segments, the apical 12 to 17 nmi. 

 long with 16 to 28 segments. While in fully developed individuals the cirri attain 

 the dimensions just given, in the individuals as collected the peripheral cirri are perhaps 

 most commonly from 35 to 50 mm. long, ^vith 32 to 45 segments. 



In the peripheral cirri the first two segments are somewhat over twice as broad 

 as long, the third is about as long as broad, the fourth is nearly twice as long as broad, 

 and the following gradually increase in length to about the eighth, which is about four 

 times as long as the median diameter, after the fourteenth to sixteenth gradually de- 

 creasing again so that the terminal segments are about twice as long as broad. The 

 penultimate segment is half again as long as broad, and gradually tapers distally. The 

 opposing spine is minute, erect, terminal; the terminal claw is slightly longer than the 

 penultimate segment, stout in the basal third but becoming very slender and nearly 

 straight distally. The fourth and following segments are moderately constricted 

 centrally, this feature becoming less marked as the segments decrease in length distally. 

 After the fifth or sLxth there is a shght dorsal overlap which becomes narrowed into a 

 small spine on the distal segments. 



The radials are just visible beyond the centrodorsal, forming a narrow even band, 

 or they may be slightly produced in the interradial angles. The IBri are veiy short 

 in the median line, usually in fully developed specimens not visible in a direct lateral 

 view because of the strong proximal process from the axillaries. The IBr2 (axillaries) 

 are shield-shaped with the borders, especially the two distal, concave, usually about 

 as long as broad but in large specimens distinctly longer than broad. 



The 10 arms are from 85 to 120 nun. (usually between 100 and 110 mm.) in length. 

 The first brachial has long outer but very short inner borders due to the deep incision 

 bj- the proximal process from the second, which sometimes in a direct lateral view 

 completely conceals it in the median hne. The second brachial is almost triangular. 

 The third and fourth brachials together form a syzj^gial pair which is approximately 

 oblong, and nearly or quite twice as broad as long. The following brachials are wedge- 

 shaped, somewhat over twice as broad as long in the median hne, after the second 

 syzygial pair becoming almost or quite triangular, at first somewhat broader than 

 long, then as long as broad, and wedge-shaped and elongate distally. 



Sj-zj'gies occur usually between brachials 3+4, 9 + 10, and 14 + 15, and distally 

 at intervals of about 4 muscular articulations. The second syzygj- exceptionally is 

 found between brachials 10 + 11, and the third between brachials 13 + 14, or more 

 commonly between brachials 15 + 16. Carpenter and Grieg have determined the 

 distal intcrsyzygial interval in 1,174 cases; they found 4 muscular articulations 627 

 times, 3 muscular articulations 398 times, 5 muscular articulations 109 times, 6 muscular 

 articulations 35 times, and 7 muscular articulations 5 times. 



Pi is very slender, from 11 to 20 mm. (usually between 12 and 15 mm.) in length, 

 composed of 25 to 45 (usually 30 to 35) segments, of which the basal five to seven 



