136 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



History. The type specimen of this species from Albatross station 4107 was 

 recorded in 1908 as a "small ten-armed specimen" of Thalassometra (Cosmiometra) 

 crassicirra. It is included under the name Cosmiometra crassicirra in the references to 

 that species published in 1909, 1912, and 1918. Just why this highly distinctive and 

 utterly different species should have been regarded as the young of Cosmiometra crassi- 

 cirra is not clear. 



STIREMETRA SPINICIRRA (P. H. Carpenter) 



Antedon spinicirra P. H. CARPENTER, Challenger Reports, Zool., vol. 26, pt. 60, 1888, p. 112 (descrip- 

 tion; Challenger station 164), pi. 11, figs. 1, 2. HARTLAUB, Bull. Mus. Comp. Zool., vol. 27, No. 

 4, 1895, p. 131 (systematic and bathymetrical relationships). HAMANN, Bronn's Klassen und 

 Ordnungen des Tier-Reichs, vol. 2, Abt. 3, 1907, p. 1578 (listed). A. H. CLARK, Crinoids of the 

 Indian Ocean, 1912, p. 33 (identity). 



Thalassometra spinicirra A. H. CLARK, Smithsonion Misc. Coll., vol. 50, pt. 3, 1907, p. 360 (listed). 



Stiremetra spinicirra A. H. CLARK, Proc. Biol. Soc. Washington, vol. 22, 1909, p. 15 (listed); Mem. 

 Australian Mus., vol. 4, 1911, p. 795 (locality) ; Crinoids of the Indian Ocean, 1912, p. 33 (identity), 

 p. 210 (synonymy; locality); Smithsonian Misc. Coll., vol. 61, No. 15, 1913, p. 44 (published 

 references to specimens in the B. M.; Challenger station 164); Unstalked crinoids of the Siboga- 

 Exped., 1918, p. 160 (in key; range), p. 161 (references). GISLEN, Ark. Zool., vol. 19, No. 32, 

 Feb. 20, 1928, p. 7, No. 28 (notes). 



Diagnostic features. All the cirrus segments except one or two of the basal bear 

 high, broad, and conspicuous dorsal spines; a few of the earlier cirrus segments are 

 slightly longer than broad; the axillaries are short, much broader than long; the IBr 

 series and lower brachials have a smooth dorsal surface, a prominent rounded median 

 carination, straight edges, and flattened sides; the brachials bear moderate over- 

 lapping carinated spines; and the cirri are arranged in 10 indistinct columns on the 

 centrodorsal. The arms are about 45 mm. long, and the cirri are about 17 mm. long 

 with 40-45 segments. 



Description. The centrodorsal is hemispherical or bluntly conical; judging from 

 the figure the cirrus sockets are arranged hi 10 columns of 2 each, and the surface of the 

 centrodorsal is unmodified. 



The cirri are XX-XXV, 40-45, according to the figure about 17 mm. long; 4 or 5 

 of the basal segments are slightly longer than broad, the remainder being broader than 

 long, those hi the distal half twice as broad as long; all but the basal segments (in the 

 figure all but the first) bear a high, conspicuous, and sharp dorsal spine. 



The radials are just visible beyond the centrodorsal. The IBri and IBr 2 (axil- 

 laries) are sharply convex and almost carinate; the figure shows both with a moderately 

 high carination having a longitudinally straight and transversely sharply rounded 

 crest. The IBri are partly free laterally and are but little incised by the hexagonal 

 axillaries, which are much broader than long with a more rounded dorsal surface, though 

 extending only slightly beyond the distal angles of the IBri. Both the elements of the 

 IBr series and the first brachials have straight edges and sharply flattened sides. The 

 inner sides of the second brachials and of the hypozygals of the first syzygial pair are 

 likewise slightly flattened. 



The 10 arms are probably about 45 mm. long. The second brachials are relatively 

 short and oblong, not projecting much backward into the first, though both are sharply 

 convex at their line of juncture. The next few brachials are about as long as broad, 

 and those following are obliquely quadrate, longer than broad. The later brachials 

 overlap slightly and become somewhat sharply carinate. 



