PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 631 



Localities.— B.A.N. Z.A.R.E. station 40; off Enderby Land Gat. 66°12' S., long. 

 49°37' E.); 300 meters; January 17, 1930 [John, 1939] (1 female, the holotype and 

 1 male, B.M.; 2 females, 1 immature, Austr. M.). Type locality. 



B.A.N.Z.A.R.E. station 41; off Enderby Land (lat. 65°48' S., long. o3°16' E.); 

 180-209 meters; at 200 meters, temperature — 1.77° C, salinity 34.24% o ; January 24, 

 1930 [John, 1939] (1 male, Austr. M.). 



B.A.N.Z.A.R.E. station 107; off MacRobertson Land (lat. 66°45' S., long. 62°03' 

 E.); 219 meters; February 16, 1931 [John, 1939] (1 male, 1 juvenile, B.JsL; 2 pcn- 

 tacrinoids, Austr. M.). 



ISOMETRA CHALLENGER! (A. H. Clark) 



Antedon lineata (not Antedon lineatus Poinel, 1887) P. II. Carpenter, Challenger Reports, Zoology, 

 vol. 26, pt. 60, 1888, p. 183 (description; sta. 320), pi. 13, figs. 4, 5.— Hamann, Bronn's Klassen 

 und Ordnungen des Tier-Reiehs, vol. 2, Abt. 3, 1907, p. 1579 (listed).— A. H. Clark, Proc. U.S. 

 Nat. Mus., vol. 34, 1908, p. 480 (renamed challengeri) ; Proc. Biol. Soc. Washington, vol. 21, 

 1908, p. 134 (synonym of Isometra angustipinna). — Hartlaub, Mem. Mus. Comp. Zool., vol. 

 27, No. 4, 1912, pp. 398, 399 (compared with A. [Anakidometra] armata). 



Antedon challengeri A. H. Clark, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 353 (new name for 

 Antedon lineata P. H. Carpenter, 1888, not A. lineatus Pomel, 1887); Proc. U.S. Nat. Mus., vol. 

 34, 1908, p. 480 (same). 



Isometra lineata John, Discovery Reports, vol. 18, 1938, pp. 174-176 (distinct from angustipinna; 

 redescription of holotype); fig. 13, p. 176. 



Diagnostic features. — The cirri are about XXV, w-ith up to about 30 segments, 

 of which the longest are only slightly longer than broad; P2 is shghtly smaller than Pi, 

 each having 8 to 9 segments; the fu'st genital pinnule is Ps or P7. 



Nomenclature [by A.M.C.]. — Since Pomel's name Antedon lineatus for a fossil 

 invalidated by a year A. lineata of P. H. Carpenter, A. H. Clark substituted the name 

 challengeri in 1907, but the following year submerged the name in the synonymy 

 of angustipinna. However, John (1938), after re-examining both the type specimens, 

 decided that the species are, after all, distinct. I have accordingly modified the 

 typescript. 



Description. — The centrodorsal is almost completely hidden by the stumps of the 

 broken cirri. 



The cirri are about XXV, the longest with at least 30 segments and over 16 nun. in 

 length; they have a slight distal taper. The fifth segment is the longest, sUghtly 

 longer than broad; the segments in the terminal third of the cirri are broader than long. 

 All of the segments overlap slightly on the dorsal side and the outer gradually acquire 

 a faint dorsal keel with a rather prominent dorsal spine. 



The radials are partially visible. The IBr, are oblong, not united laterally, with 

 the distal border shghtly excavated. The IBrz (axLUaries) are pentagonal and some- 

 what broader than long. Tlie elements of the IBr series are elevated in the middle 

 line, decreasing in height laterally. 



The 10 arms are about 90 mm. long. The first brachials are somewhat incised 

 by the second, which are relatively short and broad. The following brachials arc 

 smooth and obliquely wedge-shaped, becoming rather elongated toward the arm lips. 



Syzygies occur between brachials 3+4, 9+ 10, and 14 + 15, and distally at intervals 

 of from 2 to 5 (usually 3 or 4) muscular articulations. 



The length from the IBr, to the second sj'zj-gy is 9.0 mm. and the width at the first 

 syzygy is 1.5 mm. 



