316 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



about as long as broad. The more proximal segments are slightly constricted cen- 

 trally, and the penultimate bears a small and short subterminal opposing spine. 

 The terminal claw is half again as long as the penultimate segment, moderately and 

 evenly curved. 



The single adult from Siboga station 273 is a particularly fine example, with 20 

 arms 165 mm. long, the posterior arms being 120 mm. long. All of the arms are 

 grooved, despite the difference in the length. The centrodorsal exactly fills the 

 space between the radials, its surface being on precisely the same level as theirs, so 

 that its borders are difficult to detect. 



As redescribed by Miiller from notes taken by Troschel, Lamarck's type speci- 

 mens have a pentagon in the center of the dorsal surface. There are no cirri. The 

 elements of the IBr series are united by syzygy. The IIBr series are 2 (1 +2). The 

 arms are 20-22, but normally 20, in number, 135 mm. long. They are stout, and the 

 lateral borders of the brachials are straight. The intersyzygial interval is 4-6 mus- 

 cular articulations. The first pinnules are very long, and those following decrease 

 only slightly in size to the arm tips. 



The specimen without locality in the British Museum is a fine example, with 21 

 arms. The centrodorsal is stellate and sunken to the level of the dorsal surface of 

 the radials. There are no subradial clefts. The single IIIBr series is externally 

 developed and resembles the IIBr series. 



Abnormal specimens. The Challenger dredged a 4-rayed individual in which 

 the anterior ray is missing, so that the mouth lies in an interradius directly opposite 

 that in which the anus is situated. 



In a Challenger specimen recorded by Carpenter one of the postradial series 

 lack IIBr series, so that it bears simply 2 undivided arms, the total number of arms 

 in the individual being 18 instead of the usual 20. In this postradial series the 

 IBri is absent. On one of the 2 arms there is a syzygy between brachials 3 + 4 in 

 addition to the usual syzygy between brachials 1+2, as is normally the case in the 

 outer arms arising from IIBr series. 



Localities. Holothuria Bank, northwestern Australia; 62 meters [A. H. Clark, 

 1913] (1,B. M.). 



Holothuria Bank [A. H. Clark, 1913] (1, B. M.). 



Holothuria Bank, 69.4 meters [A. H. Clark, 1911, 1913] (3 young, B. M.). 



Baudin Island, 14.6-27.4 meters [A. H. Clark, 1911, 1913] (2 young, B. M.). 



Northwest Australia; this includes the four preceding localities; 14.6-27.4 meters 

 [Bell, 1894]. 



Thursday Island [Bell, 1884]. Same [Doderlein, 1898]. 



Challenger station 187; off Booby Island, Torres Straits (lat. 10 36' S., long. 

 141 55' E.); 10.9 meters, coral mud; September 9, 1874 [P. H. Carpenter, 1888; 

 A. H. Clark, 1913] (12, B. M.). 



Challenger station 186; Prince of Wales Channel, Torres Straits (lat. 10 30' S., 

 long. 142 18' E.); 14.6 meters; coral mud; September 8, 1874 (1, M. C. Z., 201). 



Alert; Prince of Wales Channel, Torres Straits; 9.1-12.8 meters [Bell, 1884; 

 P. H. Carpenter, 1888; A. H. Clark, 1913] (2, B. M.). 



