PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 593 



Type species. Psathyrometra antarctica A. H. Clark, 1915. 



Geographical range. Known from the Antarctic in the vicinity of Gaussherg and 

 southeast of the South Orkney Islands in the Weddell Sea. 



Bathymetrical range. Only known from 2725 and 3426 meters. 



KEY TO THE SPECIES OF EOMETRA 



a 1 . Cirri with 26-31 segments, the longest of which are at least five times as long as broad; PI slender 

 and delicate, with 11-12 segments, of which the fourth and fifth are four times as long as broad; 

 no interradial processes on the radials (near Gaussberg; 2725 meters) antarctica (p. 693) 



a'. Cirri probably with about 18 segments of which the longest are four times as long as broad; PI 

 tapering distally, the fourth and fifth of the 10 segments three times as long as broad; the radials 

 produced interradially alongside the IBri (Weddell Sea; 3426 meters) weddelli (p. 594) 



EOMETRA ANTARCTICA (A. H. Clark) 



[See vol. 1, pt. 2, fig. 765, p. 362] 



Psathyromelra antarctica A. H. CLARK, Journ. Washington Acad. Sci., vol. 5, 1915, No. 3, p. 81 

 (Antarctic; range; nomen nudum); Die Crinolden der Antarktis, 1915, p. 104 (collected by the 

 Gauss), p. 107 (in key), p. 116 (detailed description; Antarctic, 2725 meters; comparison with 

 related species), p. 170 (deep water Antarctic species to south of the Indian Ocean), p. 171 (sys- 

 tematic and geographical relationships), pi. 2, figs. 1, 2; Unstalked crinoids of the Siboga-Exped., 

 1918, p. 225 (in key), p. 230 (references) ; Smithsonian Misc. Coll., vol. 72, 1921, No. 7. pi. 2, fig. 23. 



Eometra antarctica A. H. CLARK, Proc. U.S. Nat Mus., vol. 83, 1936, p. 248 (type species of new genus 

 Eometra). JOHN, in Vaney and John, Sci. Res. Voy. Scotia, 1902-04, Crinoidea, 1939, p. 669 

 (comparison with E. weddelli). A. H. CLARK, Mem. Soc. Cubana Hist. Nat., vol. 14, No. 2, 1940, 

 p. 140. TORTONESE, Bull. Inst. Oc&mogr. Monaco, No. 956, 1949, p. 4 (depth range). 



Diagnostic features. The centrodorsal has the height about equal to the basal 

 diameter, which is 2.5 mm. in the type specimen; the cirri are about XX, 26-31 and from 

 30 to 45 mm. in length; the radials are short with no interradial processes; PI is delicate, 

 about 5 mm. long, with 11 to 12 segments, of which the fourth and fifth are four tunes 

 as long as broad; Pj is 6.5 mm. long, with 13 to 15 segments and P 3 is even longer, about 

 twice as long as P]. 



Description. The centrodorsal is small, rounded conical, about 2.5 mm. in diam- 

 eter at the base and about 2.5 mm. high, with the base hi dorsal view rounded pentagonal 

 in outline. The cirrus sockets, which almost completely cover the sides of the centro- 

 dorsal, are closely crowded, and are arranged in 10 columns of 2 or 3 each. 



The cirri are XX, 26-31, from 30 to 45 mm. long, slender with greatly elongated 

 segments and distally tapering to a fine point. In general they resemble the cirri of 

 such species as Pentametrocrinus varians or P. japonicus. The first segment is about 

 4 times as broad as long and the following gradually increase in length to the third, 

 which is half again as broad as long, the fourth, which is half again as long as the median 

 width, and the fifth, which is about 3 times as long as the median width; the following 

 segments are much elongated. In the distal third the cirri gradually taper to a point. 

 There are no dorsal processes. The terminal claw is small and conical. 



The radials are short, about 4 times as broad as long in the median line. The 

 IBr! are about 4 tunes as broad as long in the median line, moderately arched dorsully, 

 with the laterodistal angles broadly rounded off; the distal border is incised by a prox- 

 imal process from the axillary. The IBri (axillaries) are about as long as broad witli all 

 the sides rather strongly concave, the distal and proximal angles equal and similar, and 

 the synarthrial tubercles broad and rounded. 



