242 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



Antedon nematcdon HARTLAUB, Nachr. Ges. Gottingen, May 1890, p. 185 (description; Bowen, 

 Queensland). HARTLAUB, Nova Acta Acad. German, vol. 58, No. 1, 1891, p. 19 (in key), 

 p. 27 (detailed description and comparisons; Bowen), pi. 1, fig. 9. HAMANN, Bronns Klassen 

 und Ordnungen des Tier-Reichs, vol. 2, Abt. 3, 1907, p. 1582 (listed), pi. 12, fig. 6 (from Hart- 

 laub). A. H. CLARK, Vid. Medd. Nat. Foren. K0benhavn, 1909, p. 117 (identity); Mem. Aus- 

 tralian Mus., vol. 4, 1911, p. 718 (identity); Smithsonian Misc. Coll., vol. 60, No. 10, 1912, 

 p. 2 (identity); Crinoids of the Indian Ocean, 1912, p. 37 (identity). 



Himerometra nematodon A. H. CLARK, Smithsonian Misc. Coll., vol. 50, 1907, p. 356 (listed). 



Heterometra nematodon A. H. CLARK, Die Fauna Sudwest-Australiens, vol. 3, Lief. 13, 1911, p. 441 

 (Australian tropical species occurring south to Port Molle), p. 443 (range on the east coast); 

 Mem. Australian Mus., vol. 4, 1911, p. 718 (identity), p. 721 (occurs south to Bowen), p. 734 

 (in key), p. 768 (synonymy; characters; Australian record; Port Molle, Alert); Crinoids of the 

 Indian Ocean, 1912, p. 37 (identity), p. 120 (synonymy; localities). REICHENSPERGER, Abh. 

 Senck. naturf. Ges., vol. 35, Heft 1, 1913, p. 82 (Aru Islands), p. 101 (localities; notes). A. H. 

 CLARK, Unstalked crinoids of the Sfboi/o-Exped., 1918, p. 76 (in key; range). H. L. CLARK, The 

 echinoderm fauna of Torres Strait, 1921, p. 192 (distribution). GISLEN, Kungl. Fysiogr. 

 Sallsk. Handl., new ser., vol. 45, No. 11, 1934, pp. 27, 30. 



Amphimetra nematodon A. H. CLARK, Smithsonian Misc. Coll., vol. 60, No. 10, 1912, p. 2 (identity), 

 p. 15 (detailed description of the type; Bowen), p. 16 (compared with A. [Heterometra] pfiili- 

 berti); vol. 61, No. 15, 1913, p. 23 (published reference to specimen in B. M.; Port Molle, 12-20 

 fathoms) ; Internat. Revue gesamt. Hydrobiol. und Hydrogr., 1915, pp. 224 ff . (detailed account 

 of distribution in Australia). 



Diagnostic features. The enlarged proximal pinnules are slender and smooth, 

 without carinate processes on the basal segments, and are composed of 26-30 segments. 

 PI, P 2 , and P 3 are of about the same size, or P! is the longest and P 3 the shortest, 

 but P! is always larger than P D . The cirri are 25-30 mm. long and are composed of 

 40-50 segments, which are subequal, the outer bearing prominent, though not 

 especially long, dorsal spines. The 27-48 arms are 105-115 mm. long. 



Description. The centrodorsal is a thick convex disk with the cirri arranged in 

 two and a partial third irregular rows. 



The cirri are about XXX, 40-50, about 25 mm. long. The segments are approxi- 

 mately similar, none of them being longer than broad. In the distal two-thirds, or at 

 the least in the distal half, of the cirri the segments bear rather strong dorsal spines. 

 The cirri are rather strongly compressed laterally at their ends. 



The radials are not visible. The IBr t are very short, and are entirely free laterally. 

 The IBr 2 (axillaries) are almost triangular and are also very short. The IIBr series 

 are 4 (3+4), exceptionally 2. The IIIBr series are 2, but 4 (3+4) when following 

 IIBr 2 series. The IVBr series are 2, but only a few are present. The elements of the 

 IIBr and subsequent series are, when compared with the elements of the IBr series, 

 rather long. The first ossicles following an axillary are almost entirely united 

 interiorly. 



The 38 arms are more than 80 mm. long. They are composed of short discoidal 

 brachials the distal ends of which are rather strongly produced, and which in the 

 proximal third of the arms overlap somewhat laterally. Only the basal brachials have 

 smooth ends. The arms are somewhat compressed with a narrow dorsal surface. 



The first syzygy occurs between brachials 3+4, and the second from brachials 

 23 + 24 onward, often about brachials 31+32, but also further on, about brachials 

 41+42. The distal intersyzygial interval is 13 to 21 muscular articulations. 



