64 Proceedings of the Biological Society of Washington. 



appears to be a low broadly rounded dorsal spine on each segment which 

 arises from somewhat more than the distal half of the dorsal surface of 

 the segments. In the more compressed distal segments the produced 

 distal dorsal edge, at first crescentic in end view, becomes narrower, but 

 does not lose in height, so that it changes to rounded triangular and, as 

 less of the dorsal surface is involved, appears tubercular; a faint median 

 carination is traceable on the distal half of the later segments ; the oppos- 

 ing spine is very low, median in position, involving the entire surface of 

 the penultimate segment; the terminal claw is slightly longer than the 

 penultimate segment, rather slender, and moderately curved. 



The ends of the basal rays are just visible in the angles of the calyx; 

 the radials are only slightly visible in the angles of the calyx over the 

 ends of the basal rays ; the I Br : are exceedingly short and band-like, in 

 lateral apposition for rather more than their basal half but separated by 

 a U-shaped gap anteriorly; theIBr 2 are broadly pentagonal, the lateral 

 edges about as long as those of the I Br 1; approximately twice as broad 

 as long; the II Br are 2; the I Br axillary and the elements of the II Br 

 series are rounded dorsally and laterally, and entirely free laterally; the 

 synarthrial tubercles are broad and low, though rather noticeable. 



There are nineteen arms in the type, about 120 mm. long; the first two 

 brachials are equal and similar in shape, slightly wedge-shaped, the longer 

 side out, about twice as broad as the exterior length; the first brachial, 

 like the II Brj , is interiorly united for nearly its entire length ; the 

 second, like the II Br 2 , is usually interiorly in apposition with its neigh- 

 bor, though not united to it; the first syzygial pair (formed of the third 

 and fourth brachials) is about as long as broad; the fifth and sixth 

 brachials are oblong, about twice as broad as long, the following brachials 

 become very oblique, and after the eighth or ninth triangular, about as 

 long as broad, later becoming wedge-shaped, and somewhat less oblique 

 distally ; the terminal portion of the arms is not preserved. The ossicles 

 of the I Br and II Br series and the first two brachials have the dorsal 

 surface thickly covered with small shallow pits; the distal edge of the 

 second brachial is everted and somewhat prominent, tending to form a 

 rounded distal dorsal prominence which is thickly beset with small 

 spines; this condition rapidly increases distally, the brachials after the 

 eighth having strongly produced distal ends which are armed with a 

 frill of rather coarse spines, these produced distal ends standing out 

 nearly perpendicularly to the axis of the arm ; with the gradual narrow- 

 ing of the arm distally this eversion of the distal ends of the brachials 

 gradually narrows, but does not decrease in height, so that on the later 

 brachials it appears as a laterally oblong distal tubercle with the summit 

 thickly studded with small spines standing vertically outward and reach- 

 ing rather more than half the lateral diameter of the brachials in height. 

 In lateral view these tubercles appear as rounded distal spines, the gen- 

 eral effect being the same as in the more carinate varieties of Tropio- 

 metra picta. 



Syzygies occur between the first and second brachials, again always 

 between the third and fourth ; the next syzygy is almost always between 



