420 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



PTEBOMETRA SPLENDIDA (A. H. Clark) 



Ptilomelra splendida A. H. Clark, Proc. U. S. Nat. Mus., vol. 37, 1909, p. 33 (description; Albatross 



station 5179). 

 Plerometra splendida A. H. Clark, Crinoids of the Indian Ocean, 1912, p. 190 (s3'nonymy; locality); 



Unstalked crinoids of the Si6oga-Exped., 1918, p. 143 (in key; range). 



Diagnostic features. — The earlier cirrus segments have the ventral portion of the 

 distal edge raised and overlapping the bases of the segments succeeding with the 

 midventral portion produced into a long sharp spine ; the radial ring and the ring formed 

 by the IBrj are narrow and constricted, approxunately cylindrical, appearing dispro- 

 portionately small; beyond the IBrj the proximal portion of the animal is broad, the 

 profiles of the division series and arm bases diverging at an angle of about 90°: the 

 cirri are XXX, 86, 50 nmi. long; the 30 arms are 80 mm. long. 



Description. — ^The centrodorsal is columnar, 3 mm. in diameter at the base and 

 4 mm. high, with the center of the dorsal pole concave and surrounded by five broad 

 low radially situated tubercles. The cirrus sockets are arranged in 10 evenly spaced 

 columns, usually three to a column. 



The cirri are XXX, 86, very long and slender and tapering slightly distally, 

 50 mm. in length. The first segment is short, the second is twice as broad as long, 

 and those foUowmg gradually increase in length to the fifth or sLxth, which is about 

 as long as broad, and stUl further increase to the thirteenth or seventeenth, which is 

 about half again as long as broad. After the nineteenth to twenty-sixth the segments 

 decrease rather rapidly in length, soon becoming twice as broad as long, and even 

 shorter teminally. The segments from about the seventh or eighth to about the 

 twenty-fifth have the median portion of the distal ventral edge produced into a long 

 slender curved overlapping spine, this reaching a maximum size on the tenth-thirteenth 

 segments and then gradually dymg away distally. As the ventral spines on the cirrus 

 segments die away a slight prominence begins to appear on the dorsal distal edge in 

 the median Ime which gradually becomes a prominent tubercle and encroaches more 

 and more upon the dorsal surface of the segments distally becoming the broad high 

 curved carinate dorsal spine characteristic of the outer segments of the cirri in all the 

 species of this genus. 



The ends of the basal rays are visible as small dorsoventrally elongate tubercles in 

 the interradial angles of the calyx. 



The basal portion of the animal has the appearance of being strongly constricted 

 and disproportionately small. The radial ring and the ring formed by the IBri 

 are very narrow, 5 mm. in diameter; from this point the width of the animal, as seen 

 in lateral view, increases rather rapidly to about the seventh brachial, where it 

 reaches 20 mm. 



The radials are short, of equal height all around the calyx, four or five times as 

 broad as long, with a trace of a broad median tubercle. The IBr, are oblong, 4 times 

 as broad as long, laterally united in the proximal half. The IBr2 (axUlaries) are very 

 broadly pentagonal, two and one-half times as broad as long, with a slightly produced 

 lateral border. Both the IBrj and the IBrj are faintly carinate. The IIBr series are 

 2. The IIIBr series are 2, developed exteriorly. The div^ision series exteriorly have 

 slightly produced ventrolateral edges. 



The 30 arms are 80 mm. long, and resemble in general those of P. trichopoda, 



