A MONOGRAPH OF THE EXISTING CRINOIDS 581 



segments, but ends rather abruptly distally ; it is so slight that the cirri appear practi- 

 cally smooth. The opposing spine is moderate in size, triangular, arising from the 

 entire dorsal surface of the penultimate segment, terminal, and directed obliquely 

 forward. The distal ends of the cirrus segments are slightly prominent. 



The radials are almost wholly concealed by the centrodorsal, being only slightly 

 visible in the interradial angles. The IB^ are very short, almost oblong, five or six 

 times as broad as long. The IBr 2 (auxiliaries) are very short, nearly or quite three times 

 as broad as long. The IIBr and IIIBr series are 2, the latter externally developed. 

 The sides of the elements of the division series are in close apposition and sharply 

 flattened. The proximal edge of the IBrj is everted and slightly scalloped. The 

 outer edges of the IBr 2 are slightly thickened and everted but smooth. The lateral 

 third of the exposed surface of both ossicles taken together bears from a dozen to a 

 dozen and a half prominent, well-rounded, and entirely separate tubercles, some of 

 which may be more or less elongate in one diameter; between the tubercular lateral 

 and smooth dorsal surface of the elements of the IBr series there is a more or less 

 marked prominent beaded ridge or row of tubercles, which, however, may be absent. 

 The sides of the ossicles of the IIBr series are modified in the same way as those of 

 the ossicles of the IBr series, but not so extensively. 



The arms are about 26 in number, 75 mm. long; the proximal outer angle of the 

 first brachial is roughened for some distance inward, and sometimes more or less 

 tuberculated. The surface of the second brachial is similarly modified but much less 

 extensively. The synarthrial tubercles are small, but rather prominent. The distal 

 edges of the brachials are only very slightly produced. 



P! is 7 mm. long, with 21 segments, tapering rather rapidly in the proximal fourth, 

 slender from that point onward, with most of the component segments about twice as 

 long as broad. P 2 is 8 mm. long, with 17-20 segments, of which the first is nearly 

 twice as broad as long, the second nearly as long as broad, the third one- third again 

 as long as broad, and the remainder about twice as long as broad; the second-fifth 

 are narrowly carmate; the pinnule is basally little, if at all, larger than PI, but it tapers 

 less rapidly and is slightly less slender distally. P 3 is 12 mm. long, with 16-18 seg- 

 ments, slightly stiffened like P 2 in Lamprometra palmata, tapering evenly from the 

 base to the tip, larger and stouter than P 2 , which more nearly resembles P!; the pro- 

 portions of the individual segments are as in P 2 ; second-fourth segments have a slight 

 narrow carinatioii. P is similar to P 3 , 9 mm. long with about 16 segments, larger, 

 longer and stouter than P 2 , and stiffened like P 3 . P 6 is 4.5-5.0 mm. long, with 15 

 segments, small and weak, evenly tapering and becoming very slender distally. The 

 following pinnules decrease gradually in size, then increase in length and become 

 very slender distally. 



The color in alcohol is white, with a faint median line of light pinkish in the 

 proximal half of the arms. 



Locality. Siboga station 51; Molo Strait, between Flores and Bindja; 69-91 

 meters; fine gray sand; or coarse sand with shells and stones; April 19, 1899 [A. H. 

 Clark, 1912, 1913, 1918] (1, Amsterdam Mus.). 



History. Mariametra tuberciilata is as yet known only from the single specimen 

 collected by the Siboga, originally described in 1912 ajicl redescribed and figured in 

 1918. 



208244 41- 39 



