378 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



not in contact basally, about four times as broad as long, rather strongly convex dor- 

 sally, with a rather prominent narrow rounded median ridge. The IBr2 (axillaries) 

 are pentagonal, nearly or quite twice as broad as long, with the lateral edges shghtly 

 shorter than those of the IBri, making with them an obtuse angle, with a narrow 

 rounded median ridge similar to that on the IBri in the proximal half. The IIBr 

 series are 2 ; the component elements have the roiuaded median ridge much less prom- 

 inent than the corresponding elements of the IBr series. 



The 20 arms are about 120 mm. long. The first brachials are small, wedge- 

 shaped, twice as broad as long exteriorly, and are almost entirely united interiorly. 

 The second brachials are considerably larger, irregularly quadrate, hke the first 

 brachials usually with a trace of a rounded median keel. The first syzygial pair 

 (composed of brachials 3+4) is oblong, half again as broad as long. The next four 

 brachials are oblong, twice as broad as long, with a low tubercle in the proximal half 

 of the median Une. The followuig two or three brachials are wedge-sliaped and those 

 succeeding are triangular, about as long as broad. The arm tips are not preserved. 

 On the lower part of the arm traces of tubercles are found on alternate sides of the me- 

 dian hne. The proximal third of the arm is somewhat compressed laterally and bears 

 on either side a shallow lateral groove. The arms increase slowty in diameter up to 

 about the twelfth brachial. From the fourth onward the brachials have moderately 

 projecting finely spinous distal edges. 



Syzygies occur between brachials 3 + 4, again between brachials 18 + 19 (rarely 

 between brachials 17 + 18 or 20+21) and distally at intervals of from 4 to 9 (usually 

 from 6 to 8) muscular articulations. 



Pi is 8 mm. long, slender and weak, with 20 segments of which the first is broad, 

 shghtly wedge-shaped, about twice as broad as the length of the proximal edge, 

 produced distally into a high rounded carinate process. The second segment is longer, 

 half again as broad as long, and bears a large fan-shaped carinate process with a 

 scalloped or dentate distal edge. The third and fourth segments are considerably 

 less in width than the second, slightly longer than broad with strong oblong carinate 

 processes. The following segments slowly increase in length becoming twice as long 

 as broad in the terminal portion of the pinnule and are without carinate processes. 

 After the second segment the pimiule is rather sharply triangular in cross section, 

 and in the distal half the distal ends of the segments project somewhat over the bases 

 of those succeeding at the angles of the prism, this feature increasing toward the tip 

 where the ends of the segments overlap all around and are more or less spinous. 

 P2 is 14 mm. long, slender but stiff, with 21 segments of which the first is broad, about 

 twice as wide as Us proximal breadth and roundedly carinate distally, the second is 

 wedge-shaped, about as long as the proximal width, with a thin carinate process 

 about twice as broad as high distally, the third is one-third again as long as broad, 

 strongly carinate distally though the carination is not quite so high as that on the 

 second segment, the fourth is twice as long as broad and carinate distally hke the third, 

 and those following are about two and one-half times as long as broad, becoming 

 shghtly longer terminally. The pinnule is strongly styliform or prismatic, the seg- 

 ments being more or less produced distally at the angles of the prism in the shape of 

 a spine overlapping the base of the segment following. The distal ends of the seg- 

 ments are somewhat prominent and finely spinuous, this feature becoming more 



