380 BULLETIN 82, UNITED STATES NATIONAL MtTSETJM 



The radials are concealed by the centrodorsal. The IBri are very short and 

 bandlike, and are closely united laterally. The IBr 2 (axillaries) are triangular, about 

 twice as broad as long. The IBr series and the first 2 brachials are in lateral contact, 

 though the latter are not laterally flattened. 



The 10 arms are 150 mm. in length. The first brachials are short and slightly 

 wedge-shaped. The second brachials are rather larger and irregularly quadrate. 

 The first syzygial pair (composed of brachials 3 + 4) is somewhat longer inwardly than 

 outwardly and about twice as broad as the interior length. The next 3 brachials 

 are approximately oblong, or somewhat wedge-shaped, nearly three times as broad as 

 long, those following becoming triangular, about as long as broad after the middle of 

 the arm, and at the extreme tip very obliquely wedge-shaped and about as long as 

 broad or somewhat longer. After the eighth the distal ends of the brachials are some- 

 what enlarged and overlap distally, though never to any great extent. There is a 

 gradual increase in the width of the arms from the base to about the fifteenth- 

 twentieth brachials, after which the arms taper away very gradually to a slender and 

 delicate tip. 



Syzygies occur between brachials 3 + 4, again from between brachials 9 + 10 to 

 between brachials 12 + 13 (usually between brachials 11 + 12), and from between 

 brachials 14 + 15 to between brachials 18+19, and distally at intervals of usually 5 

 muscular articulations. 



The mouth is interradial, and the anal tube is central. The anal area usually 

 bears a few scattered small calcareous concretions; sometimes it is more or less 

 covered with rather large concretions. 



PI is 15 mm. long, moderately stout basally, but becoming very slender after the 

 basal third. It is composed of about 40 segments, which at first are broad with the 

 corners cut away, but become about as long as broad after the tenth. The terminal 

 comb is short, with only 7 teeth which are rounded-oblong and low, not so high as the 

 width of the segments which bear them, and have their ends truncated. P 2 is 12 mm. 

 long, resembling P b but not quite so stout basally. P 3 is about 1 1 mm. long, and P 4 

 is about 10 mm. long; these pinnules resemble P 2 and have similar combs. P 6 and 

 the following pinnules are 10 mm. long, about as stout basally as those preceding but 

 tapering much more gradually and not so slender distally, and without terminal 

 combs. After the proximal third of the arm the pinnules gradually become more 

 slender, though the distal pinnules are little, if any, longer than the genital pinnules. 

 In the proximal third of the arm the pinnule segments develop strongly produced 

 dorsal ends, this production being in the form of a rounded triangle with the apex 

 central in regard to the joint surface in the basal portion, but gradually becoming 

 distal in the outer part. The distal profile of the pinnules, therefore, is very strongly 

 serrate, while the proximal profile is practically straight. In the first 4 pinnules this 

 affects only the stouter basal portion, but in the genital pinnules it is marked for 

 almost the entire length, though most so in the basal portion. Distally the relative 

 proportion of the pinnule affected becomes progressively less and less, and it is not 

 noticeable at all in the slender distal pinnules, though it may persist as a slight carina- 

 tion of the second and third pinnule segments to somewhat beyond the middle 

 of the arm. 



