PART S A MONOGRAPH OF THE EXISTING CRINOIDS 655 



d'. Pi with about 18 segments (ofif South Georgia and Clarence Island; 236-490 meters). 



longipinna antarctica (p. 656) 



(P. Pi with up to 30 segments (off Marion Island; 137 (?91) — 255 meters) exigTia (p. 658) 



C-. The first genital pinnule similar in length and number of segments to the preceding oral pinnule 



(Burdwood Bank and the Bransfiold Strait; 150-200 meters) nutrix (p. 661) 



6'. Cirri about XXX (Shag Rocks; 177 meters) rayneri (p. 664) 



PHRIXOMETRA LONGIPINNA LONGIPINNA (P. H. Carpenter) 



Antedon longipinna P. H. Carpenter, Challenger Reports, Zoology, vol. 26, pt. 60, 1888, p. 185, pi. 30, 

 figs. 1-3. — Bather, Geol. Mag., vol. 3, 1897, p. 119 (pinnules compared with tliose of A/iWencrin«s 

 recubariensis). — A. H. Clark, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 353 (listed). — 

 Hamann, Bronn's Klassen und Ordnungen des Tier-Reichs, vol. 2, Abt. 3, 1907, p. 1579. 



Thaumalometra longipinna A. II. Clark, Proc. Biol. Soc. Washington, vol. 21, 1908, p. 128 Oisted); 

 Smithsonian Misc. Coll., vol. 61, No. 15, 1913, p. 65 (published reference to specimen in the B.M.; 

 Challenger sta. 320) . 



Phrixomelra longipinna A. H. Clark, Journ. Washington Acad. Sci., vol. 7, 1917, No. 5, p. 131 (listed); 

 Uustalked Crinoids of the iSiftoffa-Exped., 1918, p. 253 (references); The Danish /nso//-Exped., 

 vol. 4, No. 5, Crinoidea, 1923, p. 43 (locality), p. 53 (in key). — John, Proc. Linn. Soc. London, 

 sess. 149, pt. 2, 1937, p. 86 (range), p. 87 (protection of brood); Discovery Reports, vol. 18, 1938, 

 p. 124, pp. 169-170 (redescription of type specimens). 



Diagnostic features. — The cirri number about XXX, with 20 to 25 segments; the 

 lower pinnules are all long, P, reaching to about the twelfth brachial and having 12 to 

 18 segments, measuring about 7 mm. in length while the first genital pinimle, usually 

 P3, has 9+ segments and is from 4 mm. long. 



Description. — The centrodorsal is rounded conical, broader than high, with about 

 30 cirrus sockets arranged in fifteen slightly irregular columns alternating in level. 



The cirri are about XXX, 20-25 (according to Carpenter). The longest segments 

 are just over twice as long as broad and slightly constricted centrally; tlie last five are 

 about as long as broad. The distal ends of the segments are slightly' produced and 

 overlapping. 



The distal edges of the radials are just visible beyond the rim of the centro- 

 dorsal. The IBri are short, laterally free, and each is deeply incised by a rounded 

 proximal projection from the IBro. The latter are rhombic, about as long as broad, 

 with a sharp distal angle which separates the inner pro-ximal angles of the first brachials. 



The 10 arms are about 20 mm. long in the largest of the three specimens. The 

 brachials are rather long, the inner ones smooth, but the outer \vith thorny distal 

 edges. 



Syzygies occm- between brachials 3 + 4, 9+10, 14 + 15, and distall.y at intervals 

 of 2 muscular articulations. 



According to Carpenter the first pinnides measured about 7 mm. and had IS seg- 

 ments. In the largest specunen all the proximal pinnules are now broken. In one of 

 the two smaller specimens a Pi of 12 segments, 5 mm. long, remains intact, also a Po 

 of 12 segments but 6 mm. long and a P3, which is the fu-st genital pinnule, of about 

 9 segments, 4 mm. long. The ambulacral furrow fu-st appeai-s on P5. The distal 

 pinnules have about 18 segments and are about 6.5 mm. long. 



The one female specimen has a marsupium alongside each ovary on the third to 

 fifth segments of the genital pimmles. Each is split open for the whole of its length, 

 exposing the embryos within, which are arranged in a single layer and number up to 30. 

 They are irregularly spherical, 0.18 to 0.24 mm. in diameter. All appear to be at the 



