100 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



ments in PI is sufficient on its own to debar paucicirra and moluccana from being con- 

 generic. At the same time the species Iridometra exquisita can be referred to Euantedon. 

 Mr. Clark (MS) had included it in Argyrometra but I think that its relatively long 

 cirri ally it with the species of this genus. 



KEY TO THE SPECIES OF EUANTEDON 



a 1 . Cirrus segments up to about 25. 



ft 1 . Cirri about XL when the arm length is 100 mm. (Tahiti) tahitiensis (p. 100) 



b 2 . Cirri about XXV when the arm length is 40 mm. (South Australia) paucicirra (p. 101) 



a 2 . Not more than 17 cirrus segments. 



6'. Longest cirrus segments about four times as long as their median widths or longer. 

 c 1 . Cirrus segments hardly at all expanded at their distal ends (Moluccas; 397 meters). 



moluccana (p. 102) 

 c 2 . Cirrus segments markedly expanded at their distal ends (Philippines; 62-142 meters). 



exquisita (p. 103) 

 6 2 . Longest cirrus segments from two to two and a half times as long as broad; antepenultimate not 



so much shorter. 

 c 1 . Cirrus segments with each end thickened and prominent; the longest cirri 13-15 mm. long 



when the arms are 60 mm. (?China; deep) sinensis (p. 105) 



c 2 . Cirrus segments not prominently swollen at the ends; cirri 8-10 mm. long when the arms are 

 SO mm. (East Indies; 2-15 meters) ---polytes (p. 106) 



EUANTEDON TAHITIENSIS A. H. Clark 



Euanledon lahiliensis A. H. CLARK, Unstalked crinoids of the Siboga-Ei\ped., 1918, p. ix (relationship 

 with E. moluccana), p. 200 (in key; range; description; Tahiti). H. L. CLARK, Rec. South 

 Australian Mus., vol. 3, No. 4, 1928, p. 370 (comparison with E. paucicirra). 



Diagnostic features. There are about XL cirri with up to 25 segments of which 

 the longest are from two and a half to three times as long as broad. The arms are 

 about 100 mm. long in the two known specimens. 



Description. Centrodorsal very low, with a relatively large, slightly convex dorsal 

 pole 1.5 mm. in diameter; cirrus sockets arranged in about three closely crowded more 

 or less irregular alternating rows. 



Cirri XL, 22-25, from 15 mm. to 20 mm. long; first segment very short, second 

 about twice as broad as long, third about as long as broad, fourth not quite twice as 

 long as the median diameter, fifth slightly longer, sixth and seventh the longest, between 

 two and two and a half tunes as long as the median diameter; the following decrease 

 very slowly in length, the fourteenth or fifteenth and those succeeding being usually 

 from a third to a half again as long as the median diameter, though sometimes only 

 slightly longer than broad; the segment preceding the antepenultimate and the ante- 

 penultimate itself become longer again, about twice as long as broad; on the segments 

 as far as the eighth, both the dorsal and ventral profiles are equally concave, so that 

 the articulations are prominent; from this point onward the dorsal profile becomes 

 progressively more and more concave, and the ventral less and less, the segments 

 beyond the twelfth or thirteenth thus have the ventral profile approximately straight, 

 and the dorsal very strongly and narrowly concave so that both ends of the segments 

 on the dorsal side appear very prominent; opposing spine very small, terminal or 

 subterminal, directed obliquely forward; terminal claw slightly shorter than the 

 penultimate segment, moderately curved. 



The distal border of the radials projects slightly beyond the rim of the centrodorsal. 



