PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 91 



twice as long interiorly as exteriorly and twice as broad as Llie median lengtli. The 

 next four brachials are very short, twice as broad as the maximum and four times as 

 broad as the median length, wedge-shaped, mth concave proximal and distal ends. 

 After the second syzygy, the brachials soon become triangular witli gently concave 

 distal borders, and about one-third broader than long. After the proximal third of 

 the arm, the brachials gradually become wedge-shaped, at about the middle of the 

 arm becoming about as long as broad and terminally elongate. 



Syzygies occur usually between brachials 3+4, 9+10, and 14 + 15, and distally at 

 intervals of from 2 to 5, most commonly 3 or 4, muscular articulations. The second 

 sj-zygy is sometimes omitted, and the position of the third is subject to some irregularity. 

 The \vidth of the first syzygy is 2.0 mm. and the length from the proximal edge of the 

 IBr, to the second syzygy is 10.0 mm. 



Pi is 12 mm. long with 13 or 14 segments, and is considerably stiffened. The 

 first segment is about as long as broad, the second is slightly trapezoidal, from half 

 agam to nearly twice as long as the width of the narrower distal end, the thu-d is twice 

 as long as broad or slightly longer, very slightly constricted centrally, the fourth is 

 three times as long as broad, the sLxth and seventh are the longest, from three to foiu- 

 times as long as broad, and the remainder are slightly shorter. The earlier segments 

 are entirely smooth. On the sixth there is a slight eversion of the distal edge which 

 on the eighth and following becomes a conspicuous stronglj^ dentate overlapping frill. 

 P2 is 13 mm. long, with 13 or 14 segments, resembling P, but tapering more gradually 

 and hence slightly stouter. P3 on some arms is 14 mm. long, with 16 segments, slightly 

 stouter than P2, but on other arms it is 11 mm. long, with 15 segments and slightly 

 less stout than P2. P4 is 9 mm. long, ^vith 14 segments, on some arms resembling the 

 preceding pinnules, but less stiffened and much more slender, and on other arms 

 resembling Pj. The next two pinnules are similar in length and number of segments 

 to P4, but are slightly stouter basally, less stiffened, and have the ends of the outer 

 segments less conspicuously everted. The distal pinnules are 12 mm. long with 17 or 

 18 segments, which in the outer portion become about four times as long as broad. 



Remarks. — In its genera! appearance this species may be described as having tlie 

 brachial structure of a very large species of Antedon, with a centrodorsal resembling 

 that of Heliometra. 



Its much larger size and more rol)ust build give it an appearance quite different 

 from that of Iridometra adrestine, but the agreement in structure is so very close that 

 it would scarcely be advisable to create another genus for it. 



Locality. — C. S. Cable; Rotti Strait, Timor; 183 meters; on the cable. [A. H. 

 Clark, 1929] (1, B.M.). 



[Note by A.M.C] The specimen from Challenger station 219 (Admiralty Islands, 

 off New Guinea (lat. 1°50' S., long. 146°42' E.); 274 meters; mud), which was named 

 Iridometra adrestine by Gislen m 1928, may prove to be the young of maxima. Though 

 the arms are only about 20 mm. long there are already XL cu-ri, whereas in adrestine 

 with arms 40 mm. long there may be only XXXII cirri; also Pj has about 14, as opposed 

 to 10, segments. 



Genus ANNAMETRA A. H. Clark 



Antedon (part) A. H. Clark, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 341. 

 Iridometra (part) A. H. Clark, Proc. Biol. Soc. Washington, vol. 21, 1908, p. 131. 

 Cominia (part) A. H. Clark, Die Crinoiden der Antarktis, 1915, p. 104. 

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