PART 5 A MONOGRAPH OF THE EXISTING CRIXOIDS 103 



IBi'i very short, about foiu- times as broad as the lateral length, which is about 

 twice the median length; the lateral edges are concave; the ossicles are just in apposition 

 basally, but diverge from each other in the interradial angles at an obtuse angle of 

 about 120°; IBr^ (axillaries) slightly broader than long, very widely separated; the 

 lateral edges are about as long as those of the IBrj, concave, diverging outward at 

 approxhnately a right angle with each other; the anterior sides are approximately at 

 right angles to each other, nearly straight; the anterior angle is only verj' slightly and 

 broadly produced; a rounded median posterior projection incises the IBri. 



The 10 arms are all broken; the size appears to be about that of an average Antedon 

 medite/ranea. First brachial very short, twice as long exterioi'ly as interiorly, the me- 

 dian length about the same as the internal; proximal third of the inner border united 

 with that of its fellow, but the distal two thirds diverge ahnost m a straight line; 

 second brachial much larger, irregularly quadrate. The structm-e of the arms is essen- 

 tially the same as that of Antedon mediterranea. The width of the first syzygy is 1.3 

 mm. and the length from the proximal edge of the IBri to 9 + 10 about 8 mm. 



Pi is from 13.5 to 16.0 mm. long, composed of from IS to 21 segments, moder- 

 ately slender and tapering evenly from the base to the delicate tip; first segment not 

 quite so long as broad, second decreases slightly in diameter distally and about as 

 long as its proximal diameter; third between two and a half and thi-ee times as long as 

 broad, the following somewhat over three times as long as broad, becoming more elon- 

 gate distally; the segments have the whole sm'face very finely spinous, and the outer 

 have very finely spinous distal ends; the articulations are very slightly swollen; P^ is 

 similar to Pi, but not quite so long; P2 is 7 mm. long, with 14 or 15 segments, much 

 more slender than Pi but otherwise similar; P3 is 5 mm. long, with 11 segments, slender 

 and weak, all but the two basal segments much elongated; P4 is 5 mm. long, with 10 

 segments, slender and weak like P3, but more slender beyond the third segment; 

 P5 is 6 mm. long, with 13 segments, slightly stouter than P4 with slightly shorter seg- 

 ments; Pe is 7.5 mm. long, with 14 segments, similar to P5 but the component segments 

 slightly shorter and with more expanded ends. 



Locality. — Siboga station 139; Molucca Passage, north of Batjan (lat. 0°11' S., 

 long. 127°25' E.); 397 meters; mud, stones and coral; August 4, 1899 [A. H. Clark, 

 1912, 1918] (1, Amsterdam M.). 



EUANTEDON EXQUISITA (A. H. Clark) 



Iridomelra exquisita A. H. Clark, Proc. U.S. Nat. Mus., vol. 36, 1909, p. 408 (description; Albatross 

 Sta. 5178); vol. 39, 1911, p. 559 {Albatross Sta. 5483); Crinoids of the Indian Ocean, 1912, p. 232 

 (synonymy; Philippine Is., 74-78 fms.); Unstalked crinoids of the Sihoffa-Exped., 1918, p. 212 

 (in key; range), p. 213 (references; notes). 



Diagnostic features. — The XI^-L cirri have up to 15 greatly elongated segments, 

 up to 6 tunes as long as the median width, with much expanded distal ends; the ante- 

 penultimate is over twice as long as wide. 



The arms are from 40 to 50 mm., and the cirri are from 10 to 12 mm. in length in 

 the four known specimens. 



Description. — The centrodorsal is low rounded conical vrith a ver^- small papillose 

 polar area; the cirrus sockets are arranged in four or five closely crowded alternating 

 rows and have rather prominent margins. There are four or five sockets along the 



