. Bulletin - United States National Museum. Science. 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 o
. Bulletin - United States National Museum. Science. 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 mm. and the length from the proximal edge of IBr, to the second syzygy is 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, to mm. long, with 14 or 15 segments. P4 measures mm. and has 16 segments. Ps is 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 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 Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not
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