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.] 



Anledon 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. HARTLABB, Bull. Mus. Comp. Zool., 

 vol. 27, No. 4, 1895, p. 131 (systematic and bathymetrical relationships) . HAMANN, Bronn's 

 Klassen und Ordmmgen 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= Thalassometra pergra- 

 cilis}. GISLEN, Ark. Zool., vol. 19, No. 32, Feb. 20, 1928, p. 7. 



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

 station 4919). 



Anledon 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). 



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

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

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

 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 Th. attenuala); 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, 1028, p. 7 (comments). 



Thalassometra 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, No. 

 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. Sci., vol. 5, No. 6, 

 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). GISLN, Ark. Zool., vol. 19A, 

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



Thalassometra 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 braehials 

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

 in 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 keel. 



The radials are scarcely visible. The IBi'i are short and sharply convex in the 

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

 IBr series and first two braehials are slightly carinate and are more-or-less fringed with 

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

 extend to the hypozygal of the first syzygial pair. According to Gisl6n they cannot 

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



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

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



