A MONOGRAPH OF THE EXISTING CRINOIDS 173 



THALASSOMETRA GRACILIS (P. H. Carpenter) 



[See vol. 1, pt. 1, fig. 363, p. 297; pt. 2, figs. 224, p. 177, 317, p. 227, 338, p. 229.] 

 Antedon gracilis P. H. Carpenter, Challenger Reports, Zoology, vol. 26, pt. 60, 1888, p. 107 (descrip- 

 tion; Challenger station 214), pi. 12, figs. 3-5, pi. 15, figs. 1-4.— 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, 

 Proc U S Nat Mus., vol. 34, 1908, p. 474 (not Solanocrinus gracilis Goldfuss; renamed A. pergra- 

 cilis); Crinoids of the Indian Ocean, 1912, p. 33 (of P. H. Carpenter, 1888= Thalassomelra pergra- 

 cilis) —Gislen, Ark. Zool., vol. 19, No. 32, Feb. 20, 1928, p. 7. 

 Antedon pubescens A. H. Clark, Proc. U. S. Nat. Mus., vol. 33, 1907, p. 139 (description; Albatross 



station 4919). . 



Antedon pergracilis A. H. Clark, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 360, footnote (new 

 name for A. gracilis P. H. Carpenter, not Solanocrinus gracilis Goldfuss) ; Proc. U. S. Nat. Mus., 

 vol. 34, 1908, p. 474 (same). 

 Thalassomelra pergracilis A. H. Clark, Smithsonian Misc. Coll., vol. 50, p. 3, 1907, p. 360 (listed; 

 new name for Antedon gracilis, preoccupied); Proc. Biol. Soc. Washington, vol. 22, 1909, p. 14 

 (listed)- Proc. Biol. Soc. Washington, vol. 22, 1909, p. 147 (compared with Th. attenuata); 

 Zool Anz vol 39 1912, p. 426 (compared with Th. perplexa) ; Crinoids of the Indian Ocean, 1912, 

 p 33 ( = Antedon gracilis P. H. Carpenter, 1888), p. 207 (synonymy; about 30 miles west of Middle 

 Andaman; about 485 fathoms; characters; summary of previous records); Smithsonian Misc. 

 Coll vol 61 No. 15, 1913, p. 46 (published reference to specimens in B. M.; Challenger station 

 214- 'compared with 'to. attenuata); Unstalked crinoids of the Siboga-Exped., 1918, p. 167 (in 

 key'; range), p. 170 (references; record from the Andaman Islands not this species).— Gislen, 

 Ark' Zool ' vol 19, No. 32, Feb. 20, 1928, p. 7 (comments). 

 Thalassomelra pubescens A. H. Clark, Smithsonian Misc. Coll., vol. 50, p. 3 1907, p. 360 (listed); 

 Proc U S Nat. Mus., vol. 34, 1908, p. 318 (southern Japan); Amer. Nat., vol. 42, No. 500, 

 1908 p 542 (belongs to a group characteristic of the oceanic area) ; Geogr. Journ., vol 32 JNo. 

 6 1908 P . 603 (same); Proc. Biol. Soc. Washington, vol. 22, 1909, p. 14 (listed); Crinoids of the 

 Indian Ocean, 1912, p. 207 (synonymy; locality); Journ. Washington Acad Sc.., vol. 5, No b, 

 1915 p 215 (southern Japanese species; range and its significance); Unstalked crinoids of the 

 Siboga-Exped., 1918, p. 168 (in key; range), p. 170 (references) .-Gislen, Ark. Zool., vol. 19A. 

 No 32 Feb 20 1928, p. 7 (probably synonymous with gracilis and hirsuta). 

 Thalassomelra gracilis Gislen, Ark. Zool., vol. 19, No. 32, Feb. 20, 1928, p. 7, No. 25 (notes and 

 comments) . 



Diagnostic features.— The elements of the division series and the lower brachials 

 have the dorsal surface thickly beset with very fine spines; and the cirri are arranged 

 m 10 definite columns on the centrodorsal. The 10 arms are 60-80 mm. long, and the 

 cirri are 30 mm. long with 50-55 segments. 



Description.— The centrodorsal is a low hemisphere with a roughened dorsal pole. 

 The cirrus sockets are arranged in 10 columns, 2 in each radial area (Gislen). 



The cirri are about XX, 50-55, reaching 30 mm. in length; a few of the segments 

 are longer than broad, and the remainder are shorter and begin to overlap dorsally so as 

 gradually to develop a sharp spinous kseL 



The radials are scarcely visible. The IBr, are short and sharply convex in he 

 middorsal line. The IBr 2 (axillaries) are broadly hexagonal. The elements of the 

 IBr series and first two brachials are slightly carinate and are more-or-less ringed *rth 

 small spines They are also somewhat "wall-sided" with straight lateral edges that 

 eTendTthe hypo^ygal of the first syzygial pair. According to Gisleu they cannot 

 be described as "very sharply flattened against each other." 



The 10 arms are about 60 mm. long. They consist of elongately quadrate brachial, 

 of which the outer overlap a little. The dorsal surface of the arms is spiny (Gisl6n). 



