A MONOGRAPH OF THE EXISTING CRINOIDS 419 



of Anledon at Amboina), p. 11 (collected by Brock at Amboina), p. 15 (at Amboina next com- 

 monest to A. ludovici), p. 39 (in key), p. 55 (Amboina; detailed description and comparisons), 

 p. 58 (in second section of the Palmata group with spiny lower pinnules), p. 113 (in Gottingen 

 Mus.), pi. 3, figs. 35, 37.— Pfeffer, Abh. Senck. naturf. Ges., vol. 25, 1900, p. 85 (Ternate).— 

 Hamann, Bronns Klassen und Ordnungen des Tier-Reichs, vol. 2, Abt. 3, 1907, p. 1581 (listed).— 

 A. H. Clark, Smithsonian Misc. Coll., vol. 60, No. 10, 1912, p. 2 (identity) ; Crinoids of the 

 Indian Ocean, 1912, p. 37 (identity). 



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



Stephanometra oxyacantha A. H. Clark, Proc. Biol. Soc. Washington, vol. 22, 1909, p. 10 (listed) ; 

 Notes Leyden Mus., vol. 33, 1911, p. 183 (Amboina); Rec. Australian Mus., vol. 9, No. 1, 1912, 

 p. 82 (detailed description of a specimen from Ugi, Solomon Islands); Smithsonian Misc. Coll., 

 vol. 60, No. 10, 1912, p. 2 (identity) , p. 19 (Amboina; description of one of the specimens recorded 

 by Hartlaub); Crinoids of the Indian Ocean, 1912, p. 37 (identity), p. 132 (synonymy; Amboina; 

 Solomon Islands). — Reichensperger, Abh. Senck. naturf. Ges., vol. 35, Heft 1, 1913, p. 83 (Am- 

 boina), p. 102 (characters of the specimens). — A. H. Clark, Unstalked crinoids of the Siboga- 

 Exped., 1918, p. 94 (in key; range; references; notes; station 99; Enkhuizen Island), pp. 272, 

 276 (listed). — Gislen, Kungl. Fysiogr. Sallsk. Handl., new ser., vol. 45, No. 11, 1934, p. 25. — 

 A. H. Clark, Temminckia, vol. 1, 1936, p. 302 (near Bongao; near Koepang; Obi latoe; Am- 

 boina; Lembeh Strait, Celebes; notes). 



Diagnostic features. — The outer cirrus segments are wholly without dorsal 

 processes, being merely more or less sharply carinate in the middorsal line; Pi is 

 flexible, flagellate, delicate, and slender, much smaller and weaker than P 2 ; P 2 , P3, 

 and P 4 , and sometimes also P 6 , are much enlarged, stiffened, and spinelike, pro- 

 gressively decreasing in length; there are 24-32 (usually 30) arms 100-150 mm. 

 long; and the cirri have 23-29 (usually about 25) segments. 



Description. — The centrodorsal is moderate in size, discoidal, with the bare polar 

 area slightly concave, 2.5 mm. in diameter. 



The cirri are XXXII, 23-24, from 20 to 25 mm. long. The first segment is short, 

 the next two are about twice as broad as long, and those following gradually increase 

 in length, becoming about as long as broad on the fifth or sixth. The next three or 

 four segments are slightly longer than broad, and those succeeding very gradually 

 decrease in length, becoming about half again as broad as long distally. The segments 

 in the proximal half of the cirri are slightly constricted centrally and have somewhat 

 prominent ends, and those in the distal half are slightly compressed laterally and may 

 be bluntly carinate. The opposing spine is median to terminal, blunt, and triangular, 

 equal in height to one-quarter the width of the penultimate segment. The terminal 

 claw is somewhat longer than the penultimate segment and is moderately slender, 

 evenly tapering, and moderately curved. 



The radials are visible only in the interradial angles. The IBr, are very short, 

 in contact basally, about four times as broad as long. The IBr 2 (axillaries) are short 

 and broad, almost triangular, twice as broad as long, with the lateral edges swollen 

 and produced into rounded lateral processes. The IIBr series are 2; the IIBr, are 

 interiorly united for about three-quarters of their length. The elements of the divi- 

 sion series and the first brachials have rounded lateral processes. In the specimen 

 described the IIIBr series are present exteriorly on three postradial series. 



The 24 arms are about 120 mm. long. The first two brachials are short, wedge- 

 shaped, twice as broad as long exteriorly, the first interiorly united for most of their 

 length. The first syzygial pair (composed of brachials 3+4) is half again as broad 



