212 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



at intervals of from 6 to 1 1 muscular articulations. The usual second syzygy may be 

 omitted, in which case the second syzygy is between brachials 13 + 14. 



P! is 3.5 mm. long with 16 segments, very strongly prismatic, very stout basally 

 but tapering rather rapidly in the proximal half, less rapidly hi the distal. The first 

 segment is much broader than long with the adoral end slightly produced and swollen 

 into a broad rounded tubercle. The second segment is longer, and also broader, than 

 the first, about three times as broad as long. The segments following slowly increase 

 in length so that the last three or four, disregarding the strong lateral processes, are 

 somewhat longer than broad. From the third segment onward the middle of the outer 

 side is conspicuously carinate; on the fifth and following this carination projects as a 

 thin keel of progressively increasing height, on the sub terminal segments reaching a 

 height equal to more than half the width of the segment. The keel at first is of uni- 

 form height, with the proximal end rounded and the distal truncated, but it soon 

 becomes highest at the distal end of the segments, its edge running in a broad curve 

 to near the base. This makes the profile of the outer portion of the pinnule very 

 deeply serrate, the proximally convex and distally straight teeth being separated by 

 intervals somewhat less than their own area. The edges of the segments toward the 

 arm tip are similarly, though not so extravagantly, modified. P 2 is nearly or quite 

 5 mm. in length, very stout, tapering rather slowly with the distal third flexible though 

 not particularly slender, composed of 13 or 14 segments of which the first is trapezoidal 

 with the distal side the longest, about three times as broad as long, the distal side 

 twice as long as the proximal. The second segment is wedge-shaped, broader than 

 the first, twice as long on the side toward the arm tip as on the adoral side, more 

 than twice as broad as the greatest length. The third segment is less strongly wedge- 

 shaped, the side toward the arm tip being only slightly longer than the adoral side; 

 it is somewhat more than twice as broad as long. The segments following have 

 parallel proximal and distal ends and very slowly increase in length distally, the small 

 terminal segments being, if the long lateral processes are disregarded, slightly longer 

 than broad. On the edge toward the arm tip the segments are produced into high 

 thin carinate processes, these processes on the second-fourth segments having the 

 profile straight and parallel to the axis of the pinnule, those on the segments following 

 having the profile convex, later becoming rounded angular, the process being very 

 high at the distal end of the segment, turning a sharp angle and running in practically 

 a straight line to the base. In the midline of the pinnule each segment bears in the 

 outer half a large very high rounded or more or less flattened tubercle directed more 

 or less toward the arm tip. On the segments in the outer half of the pinnule this 

 becomes a long process directed outward nearly as long as the width of the distal end 

 of the segment ; its distal edge continues in a straight line the distal border of the seg- 

 ment, its proximal border running inward from a sharply rounded apex to the base. 

 The distal half of the pinnule has on both sides a strongly serrate profile, the serra- 

 tions being much higher on the outer than on the inner side. Pa is 3 mm. long with 

 10-12 segments, very much more slender than P 2 , more slender and more evenly 

 tapering than P,, the segments becoming about as long as broad on the seventh and 

 twice as long as broad terminally. The pinnule is rather strongly prismatic. The 

 adoral edge of the segments is produced into a moderate thin rounded carination which 

 disappears on the small terminal segments, and the midline of all the segments beyond 



