PART 5 A MONOGRAPH OF THE EXISTING CKINOIDS 35 



The column is composed of about 19 discoidal columnals, of which those in the 

 upper half are very thin, those in the lower half becommg progressively thicker toward 

 the terminal stem plate. The column is curved so that the axes of the two ends are at 

 right angles to each other. 



The terminal stem plate is circular, large and thick, three or more times as broad 

 as the column. 



Notes.— The three specimens collected by the Hamburg Southwest Australian 

 E.xpedition in 1905 may be described as follows: 



The largest specimen has the cirri arranged in 10 closely crowded columns of two 

 (sometimes one) each. 



The cirri are XVII, 41-44, from 15 to 20 mm. long, stout basally but tapering very 

 evenly and gi'aduaUy and becoming very slender at the tip where the dorsoventral 

 \ddth is not quite half of what it is at the base. The first segment is short and those 

 following gi-adually increase in length, becoming about as long as broad on the third or 

 fom-th and, still fiu-ther increasing, becoming nearly half again as long as broad on about 

 the seventh. From this point onward the segments very slowly decrease in length, so 

 that those in the distal third of the cu-ri are about half again as broad as long. The 

 longer earlier segments show a tendency to be centrally constricted or "dice-box shaped." 

 There are no dorsal spines or projections. The opposmg spine is small, sharp, subter- 

 minal, and nearly erect. 



The 10 arms are 27 mm. long. 



Syzygies occur between brachials 3+4, 7 + 8, and 12 + 13, and distaUy at intervals 

 of 2 muscular articulations. 



Pi is 4.5 mm. long, -nath 12 segments, of which the first is about a third again as 

 broad as long, the second is about half again as long as broad, the third is shghtly over 

 twice as long as broad, and those foUo^ving are about three times as long as broad. 

 In the outer half of the pinnule the distal edges of the segments project shghtl3' dorsally. 

 The pinnule is moderately stout basally and tapers evenly and graduallj^ to the tip, 

 not being flagellate distally. It is more or less rounded prismatic. 



P2 is 3 mm. long, with 12 seginents, smaller and weaker than Pj with shorter seg- 

 ments. 



P3 is 3 mm. long and resembles Po. The pinnules following become very slender, 

 but do not increase in length. 



The borders of the disk are only vei-y shghtly concave in the interbrachial areas. 



The color is deep purple, the centrodorsal and cirri white. 



The two other specimens are similar, but slightly smaller. One has the cirri very 

 slightly purphsh at the tip, and the other has a white mediodorsal line on the arms. 



The three specimens from Fremantle are small, though mature. The arms are 

 13 mm. long, and the cirri are 9 mm. long. The longest cirrus segments are broader 

 than long. 



Dr. Clark said that the smallest individuals that he and Professor Bennett took at 

 Bunbury were hardly 20 mm. across. The longest of the dozen cm-i are about as long 

 as the arms (say 8 to 10 mm.) and have some 35 segments. The largest individuals 

 have the arms 25 to 30 mm. long and the longest of the XX-XXV cirri are but little 

 shorter; they have more than 50 segments of which the terminal dozen are very small. 

 There are only 20 to 25 pinnules on each side of the longest arms. 



