A MONOGRAPH OF THE EXISTING CRINO1DS 93 



A. H. CLARK, Unstalked Crinoids of the Siboga Exped., 1918, p. 4 (in key ; range); p. 5 

 (synonymy; detailed account; stations 43, 99, 282; Enkhuizen I.); pp. 271, 272, 275 (listed); 

 pi. 1 (colored figure). H. L. CLARK, The Echinoderm Fauna of Torres Strait, 1921, p. 8 

 (collected by the Carnegie Exped., 1913); p. 12 (Mer; Port Galera, Mindoro; color in life; 

 remarks); pp. 192 and following (range). H. L. CLARK, Journ. Linn. Soc. (Zool.), vol. 35, 

 1923, p. 231 (Abrolhos Is.); p. 232 (Long I.; characters). 



Diagnostic features. The size is very large; the cirri have 25-31 (usually 26-30) 

 segments, and are about 30 mm. long; the arms are 27-80 or more (very rarely less 

 than 40) in number, from 150 mm. to 170 mm. in length; the inner derivative from 

 each IIBr auxiliary divides like the outer. 



Description. The centrodorsal is moderately large, discoidal, with the polar 

 area from 5 to 6 mm. in diameter, slightly concave, with a rounded and usually 

 shallow median pit. The cirrus sockets are arranged in 2 or 3 closely crowded alter- 

 nating marginal rows. 



The cirri are XX-XXX, 25-31 (usually 26-30), about 30 mm. in length, long, 

 large, and usually stout. The first segment is very short, and the following gradually 

 increase in length to the sixth, which is about as long as broad; the succeeding seg- 

 ments to the tenth or eleventh are similar, and those following become shorter, 

 about twice as broad as long. The transition segment is the ninth, tenth, or eleventh. 

 In the specimens with comparatively slender cirri the cirrus segments become about 

 as long as broad on the fifth, the sixth to the twelfth being about one-third again 

 as long as broad, and the following again about as long as broad, and short distally. 

 The transition and following segments gradually develop a distal dorsal tubercle 

 which becomes quite prominent, on the outer segments gradually moving to a sub- 

 median position and becoming median on the terminal four or five. This tubercle 

 is usually blunt conical, but frequently more or less laterally elongate, especially on 

 the more proximal segments. 



The ends of the basal rays are visible as small flattened inconspicuous tubercles 

 in the angles of the calyx. 



The radials are very short in the median line, but extend far up in the angles of 

 the calyx. The IBr t are very short, oblong, usually with the proximal border slightly 

 convex, well rounded dorsally and laterally, not quite meeting basally, the lateral 

 edges of adjacent IBri diverging. The IBr 2 are very broadly pentagonal, the lateral 

 edges being about as long as those of the IBr, ; they are somewhat over twice as broad 

 as long. The lateral edges of the IBr! and IBr 2 make an obtuse angle with each other. 

 The IIBr are 2, almost invariably all present. The IIIBr series are 2, and, like the 

 IIBr series, are almost always all present. IVBr, VBr, VIBr, and rarely VIIBr 

 series are present, always 2, developed externally in reference to the IIIBr series. 

 Some individuals do not have the division carried beyond the IVBr series, though 

 usually VBr series at least are present. The division series are well separated, expos- 

 ing a strip of perisome between the postradial series, the width of which is equal to 

 about half that of the IIBr series. 



Arms 27-80 or more in number (usually 40-45), 150 to 170 mm. long. The 

 first 2 brachials are similar in size and shape, small, slightly wedge-shaped, about 

 three times as broad as long; the first are almost entirely united interiorly, as are the 

 segments immediately following each axillary. The next 5 brachials are oblong, about 



