A MONOGRAPH OF THE EXISTING CRINOIDS 



551 



triangular area between them are two incomplete and less regular columns of two or 

 three sockets each. The arrangement approaches that of Poliomelra prolixa except 

 that the centrodorsal is relatively lower and the columns are consequently shorter. 



All the cirri are lost, not even stumps remaining. 



The division series and proximal brachials are as shown in the figure and have a 

 few fine spines along their distal edges. The brachials become much more spinous 

 beyond the bases of the arms. 



The arms were over 90 mm. in length. The longest remaining is of 88 brachials 

 and measures SO mm. Syzygies are present at brachials 3+4, 9 + 10, 14 + 15 and then 

 at intervals of three (or fom-) muscular articulations. The width at the first syzygy 

 is 2.0 mm. and the length from the proximal edge of IBr, to the second syzygy is 11.0 

 mm. 



No Pi is complete beyond the second joint. 



A broken Pa with 14 segments measm-ing 9 mm. remains, but a complete one, formerly 

 concealed between the arms, was found to be very attenuate with 27 segments; it 

 measures 14 mm. The segments are longer than broad after the first three and most are 

 two to three times as long as wide. The distal ends of the longer segments are distinctly 

 flared and spinous. 



Pa tapers evenly and is much shorter, 7.5 to 8.5 mm. long, with 14 or 15 segments. 



P4 measures 9.0 mm. and has 16 segments. 



Ps is 10.5 mm. long with 17 segments. 



The distal pinnules are longer. Pis with 22 segments is 15 mm. long. It is much 

 stouter than the oral pinnules. 



Figure 31. — Hybometra senta A. H. Clark, holotype: a, Radial view of calyx; h, twentieth arm 

 segment; f, centrodorsal in interradial view; d, spicules from ambulacra of distal pinnule; e, Pj; 

 /, ?>; g, Ps; K P18. 



