PAST 5 A MONOGRAPH OF THE EXISTING CRINOIDS 533 



Diagnosis. A genus of Zenometrinae in which there are no bare interradial areas 

 with ridges, grooves or lines on the centrodorsal; the division series and brachmls are 

 smooth or barely spinous at the edges; the oral pinnules have distal segments which 

 are little longer than broad (as in the subfamily Heliometrinae) and there are no brood 

 pouches. 



Type species. Cydometra flavescens A. H. Clark, 1911. 



Geographical range. Known from the western part of the Arabian Sea and from 

 off the west coast of South Africa. 



Bathymetrical range. From 461 and 2194 meters. 



Remarks. Since the discovery of the species multicirra in 1952 and the reexami- 

 nation of the type specimen of C. flavescens, the genus Cydometra has been regarded 

 as best placed In the subfamily Zenometrinae. When first constituted it was placed 

 in the Heliometrinae on account of the short and numerous segments of the oral 

 pinnules. 



KEY TO THE SPECIES OF CYCLOMETRA 



a 1 . Cirri XL, 41-43, 30 mm. long, the longest segments twice as long as broad; PI 17-19 mm. long 

 with 42-45 segments; P> shorter, 14 mm. long w-ith 32 segments; PS 12 mm. long with 25 seg- 

 ments; arms 130 mm. long in the unique holotype (northwest of Sokotra; 2,194 meters). 



flavescens (p. 533) 



a 2 . Cirri LXXX, 31, 40 mm. long, the longest segments nearly or quite three times as long as broad; 

 P! 15 mm. long with 33-34 segments; Pj stouter and slightly longer with 24-27 segments; Pi 

 10 mm. long with 17-19 segments; arms about 100 mm. long in the unique holotype (west coast 

 of the Cape of Good Hope; 461 meters) multicirra (p. 534) 



CYCLOMETRA FLAVESCENS A. H. Clark 



Cydometra flavescens A. H. CLARK, Proc. U.S. Nat. Mus., vol. 40, 1911, p. 51 (nomen nudum; locality); 

 Proc. Biol. Soc. Washington, vol. 24, 1911, p. 87 (description; locality); Crinoids of the Indian 

 Ocean, 1912, p. 239 (description; locality); Smithsonian Misc. Coll., vol. 61, 1913, No. 15, p. 64 

 (references to the specimen in the B. M.; locality); Die Crinoiden der Antarktis, 1915, p. 126 

 (range); Unstalked crinoids of the St&oi/a-Exped., 1918, p. 244 (in key; references); John Murray 

 Exped. 1933-34, Sci. Reports, vol. 4, No. 4, 1937, p. 102 (references; locality), p. 104 (listed), 

 p. 105. A. M. CLARK, Trans. Roy. Soc. South Africa, vol. 33, pt. 2, 1952, pp. 191-192 (supple- 

 mentary description); fig. 1, p. 192 (centrodorsal). 



Diagnostic features. The cirri are about XL when the arms are 130 mm. in length, 

 arranged in three columns of two or three cirri in each radius; the longest cirrus seg- 

 ments are about twice as long as broad; PI is very long, with 42Ht5 segments and meas- 

 ures about 18 mm., the distal segments being little longer than broad; the following 

 pinnules are shorter. 



Description. The centrodorsal is rounded conical, 4 mm. broad ut the base and 

 2.7 mm. high. The cirrus sockets are arranged in 15 columns of 2 or 3 each. 



The cirri are XL, 41-43, 30 mm. long. The first segment is short, the second is 

 nearly as long as broad, and those following gradually increase in length, becoming 

 twice as long as broad on the fourth. The next five are similar and those succeeding 

 gradually decrease in length after about six more, becoming about as long as broad 

 and maintaining a similar proportion until the end of tire cirrus. The earlier segments 

 are slightly constricted centrally with the ends all around finely spinous. The short 

 outer segments are carinate, the carinatiou appearing smoothly convex in lateral view. 

 The opposing spine is quite conspicuous. The terminal claw is slightly curved and 

 almost equals in length the penultimate segment. 



