314 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



Antedon rhomboidea (not of P. H. Carpenter, 1888) HARTLAUB, Bull. Mus. Comp. Zool., vol. 27, No. 4, 

 1895, p. 137 (range), p. 138 (detailed description of a specimen from Albatross sta. 3357, except 

 of the cirri and pinnules which are from a specimen from sta. 3424; discussion [example from 

 Smyth's Chnim<i\ = magellanica]), pi. 1, figs. 1-3, 6, 10, 11, pi. 2, figs. 12, 14, 15, 17, pi. 3, fig. 24. 



Heliometra tanneri A. H. CLARK, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 351 (listed). 



Heliometra rhomboidea A. H. CLAHK, Bull. Mus. Comp. Zool., vol. 51, No. 8, 1908, p. 238 (Albatross, 

 stas. 4621, 4622, 4630), p. 239 (tactile cirri). 



Florometra tanneri A. H. CLARK, Die Crinoiden der Antarktis, 1915, p. 138 (Albatross sta. 3385) ; 

 Unstalked crinoids of the Siboga-Exped., 1918, p. 241 (in key; range), p. 243 (references), p. 244 

 (discussion). GISLN, Zool. Bidrag Uppsala, vol. 9, 1924, p. 18 (abnormal arm structure). 



Florometra magellanica (not of Bell, 1882) A. H. CLARK, Die Crinoiden der Antarktis, 1915, p. 138 

 (Albatross stas. 3357, 3424, 4621, 4622, 4630). 



Promachocrinus (Florometra) magellanica A. H. CLAHK, Die Crinoiden der Antarktis, 1915, p. 142 (in 

 part; Panama records). 



Diagnostic features. A species of Florometra in which there are no carinate proc- 

 esses on the basal segments of the proximal pinnules which therefore appear very 

 slender. The middle and distal pinnules are also more slender with more elongate 

 segments than those of any of the other species in the genus. The third syzygy is usually 

 between brachials 16 + 17. 



With this species there occurs Fariometra parvula, which is very easily mistaken for 

 its young. In F. parvula, however, the centrodorsal is sharply conical, and the distal 

 intersyzygial interval is only 2 muscular articulations, while the third syzygy is between 

 brachials 14 + 15. 



Description. The centrodorsal is flattened hemispherical with a more or less deep 

 depression at the dorsal pole; the cirrus sockets, which completely cover the sides, are 

 arranged in 4 or 5 alternating rows. 



The cirri are about LX, 40-54, 60 mm. long; the fourth-tenth segments are elongated, 

 and the following to the twentieth are longer than broad. Beyond the eighth segment 

 the cirri are strongly compressed laterally. In the distal half the dorsal ends of the 

 segments are produced into a small spine. 



The radials are even with the rim of the centrodorsal, or extend for a very slight 

 distance beyond it. The IBr! are very short, not in lateral contact with each other, 

 with converging sides; there is a strong rounded synarthrial tubercle on the line of 

 union with the axillaries which is scarcely marked in the younger individuals. The 

 IBr 2 (axillaries) are moderately large and triangular; the proximal border is markedly 

 broader than the distal edge of the IBr^ 



The 10 arms are from 150 to 155+ mm. in length (in the specimens from stas. 

 4630 and 3357). The first brachials are short, not in contact with each other interiorly; 

 there is a strong synarthrial tubercle on the line of union with the second brachials, 

 which are approximately triangular. The first syzygial pair (composed of brachials 

 3+4) is roughly oblong. The following brachials to the second syzygial pair are of 

 almost the same length, but more wedge-shaped. After the second syzygial pair there 

 are two or three shorter discoidal brachials after which they become markedly tri- 

 angular. In the distal half of the arms where the brachials have the distal ends 

 thickened, finely spinous and overlapping, their form becomes again more wedge-shaped. 

 Articular tubercles, less strongly developed than the synarthrial tubercles between 

 the first two brachials, occur as far as the tenth or eleventh brachials. 



