460 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



2 or 3 before the penultimate are nearly or quite twice as broad as long. The ninth 

 or tenth is a transition segment with a narrow terminal band light in color and with 

 a highly polished surface like the following segments. On the transition segment 

 there is a slight thickening of the dorsal portion of the distal edge which on the 6 

 or 7 preceding the penultimate becomes a small pointed conical terminal dorsal 

 tubercle. The opposing spine is small, but little larger than the tubercles on the 

 preceding segments, conical, arising from the entire dorsal surface of the penultimate 

 segment, with the apex median to subterminal. The terminal claw is from half 

 again to twice as long as the penultimate segment, moderately stout, evenly tapering 

 and evenly curved, or more strongly tapering and more strongly curved in the proximal 

 half than distally. 



The ends of the basal rays are visible as minute tubercles in the interradial 

 angles. 



Very little, if any, of the dorsal surface of the radials is concealed by the centro- 

 dorsal. The radials are short, their distal width being about four times their length; 

 their distal border is concave, and the anterolateral angles are broadly rounded. The 

 IBr t are short and broad, about twice as long as the radials, five or six times as broad 

 distally as the median length, with the distal border straight. The proximal two- 

 thirds or three-fourths of the lateral borders of adjacent IBr, are united, these borders 

 beyond the point of union diverging at usually a right angle. The IBr 2 (axillaries) 

 are triangular with the lateral angles slightly truncated, twice as broad as long. 

 The anterior angle is approximately a right angle, and the anterior sides are almost 

 straight. The IIBr series are broad, 4 (3+4), or exceptionally 2. Interiorly the 

 first 2 elements are in lateral contact, but the syzygial pairs are free. Exteriorly the 

 IIBr series on adjacent rays are separated by a space equal to from one-quarter to 

 one-half of their width. The IIlBr series are 2 exteriorly, and 4 (3 + 4) interiorly; 

 but this order is reversed following IIBr 2 series. The IVBr series are 2. The 

 VBr series are 2, or rarely 4 (3 + 4). The VIBr series are 4 (3 + 4), but are seldom 

 developed. Beyond the IIIBr axillary, which bears on the inner face a IVBr 2 series 

 and on the outer an undivided arm, the succeeding axillaries typically bear on one 

 face a division series and on the other an undivided arm, which alternate in position 

 in the successive divisions. 



The dorsal perisome is completely covered with unusally solid plates which 

 are very irregular in size and arrangement. There may be between the IIBr series 

 on adjacent rays 2 or 3 large plates, or a single plate resting on the anterolateral angles 

 of the IBr] which is followed by 2 columns of polygonal plates, or simply a mass of 

 plates of various sizes showing no definite arrangement. The plating between the 

 IIBr series on adjacent rays runs distally and tapers to a point between the basal 

 segments of P D . Interiorly the IIBr series are connected by a narrow strip of heavily 

 plated perisome. 



The arms are 65-150 or more in number, from 105 to 215 mm. in length. They 

 are narrow at the base, slowly increasing in width to about the fifteenth brachial 

 and thence tapering distally, this feature being much more noticeable on some arms 

 than it is on others. The first 2 brachials are approximately equal in size and shape, 

 slightly wedge-shaped, twice as broad as long. The first brachials are interiorly 



