A MONOGRAPH OF THE EXISTING CRINOIDS 91 



the lower brachials are somewhat compressed laterally. The arm now becomes more 

 rounded, and the brachials become triangular, distally again becoming rectangular. 

 From about the twentieth brachial onward the distal ends are rather strongly pro- 

 duced. 



The first three pinnules are similar in structure, stout, almost always more strongly 

 keeled than those succeeding, tapering evenly distally and running to a sharp point. 

 P! and P 2 scarcely differ. In the largest specimen P x measures 6.5 mm. in length and 

 is composed of 16-21 segments, which to about the seventh are broader than long, 

 the third-sixth being about twice as broad as long; the distal segments are very 

 slender, and are up to 3 times as long as broad. P 2 is 7 mm. long and is composed of 

 18-20 segments, of which the six lowest are from broader than long to about as long 

 as broad, and those following become longer than broad. P 3 is 5 mm. long, with 15-17 

 segments, of which the relations are as in P 2 . P 4 is shorter, stiff, and straight, with 

 broader proximal segments and rapidly tapering distal segments; it measures 3.3 mm. 

 in length and is composed of 14-16 segments. P 6 is the shortest pinnule on the arm; 

 it measures from 3 mm. to 3.1 mm. in length and is composed of 10-13 segments. 

 P„ is about 3.5 mm. long, and the pinnules following gradually increase to a length of 

 5 mm. The disk is thickly studded with calcareous granules, which vary from wart- 

 like to pointed. The high cylindrical anal tube and the ambulacra of the disk are 

 prominently plated. The disk measures 5-7 mm. in diameter. 



In Doderlein's specimen from Thursday Island there are 51 arms. The cirri are 

 XLII, about 44; the segments in the distal third of the cirri have dorsal spines. 

 Syzygies occur between brachials 3 + 4, again from between brachials 27 + 28 to be- 

 tween brachials 29+30, between brachials 43+44, 55 + 56, and so on. P! and P 2 

 are about equal in length. P, has about 25 and P 2 about 37 segments. P 3 is shorter 

 than the preceding pinnules and is composed of about 25 segments. There is no 

 plating on the disk. The color is whitish, each segment of the division series, arms, 

 cirri, and proximal pinnules bearing a transverse stripe often broken up into spots. 

 Only a few cirri are dark brown to the tip. Doderlein remarked that although the 

 number of arms is less than in the specimens described by Bell and Carpenter, and the 

 fifth forking of the postradial series mentioned by Carpenter as a specific character is 

 not present, he has no doubt that this specimen really belongs to the present species. 



The detached disk from Cape York in the Hamburg Museum, which was described 

 by Lov6n under the name of Hyponome sarsi, presents no characters by which it may 

 be distinguished from a detached disk of this species, in which, as in all the species 

 of the family, the disk is very easily lost. On the other hand, there is no way by which 

 a detached disk could be definitely determined as of this species. 



In the Challenger specimen from station 186, as described by Dr. P. H. Carpenter, 

 the centrodorsal is relatively large with the dorsal surface slightly convex and free 

 of cirri. The cirrus sockets are arranged in about three rows. The cirri have 40-45 

 segments, few or none of which are longer than broad and the distal are quite short 

 with tolerably well-marked dorsal spines, the opposing spine being sharp and distinct. 

 The radials are barely visible. The elements of the IBr series are united by syzygy. 

 The postradial series divide 4 and sometimes 5 times. Except for the IBr series, all 

 the division series are 4 (3+4). The brachials are smooth, the proximal short and 

 nearly triangular, those after about the sixtieth becoming more oblong. Syzygies 



