A MONOGRAPH OF THE EXISTING CRINOIDS 215 



The disk is 10 mm. in diameter, not much plated except along the ambulacra. 

 There is a strong covering of plates over the gonads, with numerous sacculi imbedded 

 in it. The later pinnules have a well-defined ambulacral skeleton, the sacculi alternat- 

 ing with the side plates. 



The color in alcohol is a light whitish brown with a brownish gray ventral perisome. 



Notes. Carpenter gave the expanse of the specimen he described as 55 cm., which 

 is equivalent to an arm length of 275 mm. But his figure shows a specimen with an 

 arm length of about 250 mm., at an enlargement of \% times, which, corrected, gives an 

 arm length of 176 mm. Apparently, therefore, the expanse as given, 55 cm., is a 

 typographical error for 35 cm. 



I examined two fine specimens from Carpenter's type series at the British Museum 

 and found this to be a large, robust, and handsome species. 



After examining the same specimens Prof. Torsten Gislen wrote that the centro- 

 dorsal is a high cone. The cirri are in 10 columns, and are without dorsal spines. 

 The opposing spine is forked or transverse. The genital pinnules have rather much 

 expanded segments. 



Locality. Challenger station 192; near the Kei Islands (lat. 549'15" S., long. 

 13214'15" E.); 256 meters; blue mud; September 26, 1874 [von Graff, 1887; P. H. 

 Carpenter, 1888; Hartlaub, 1895, 1912; Minckert, 1905; A. H. Clark, 1907, 1909, 1911, 

 1912, 1913, 1916, 1918; Gisldn, 1928] (2, B. M.). 



History. Prof. Ludwig von Graff in the Challenger report on the myzostomes 

 published in 1887 mentioned Antedon flexilis as a host of certain species. The name, 

 which had been given him by Dr. P. H. Carpenter, was a nomen nudum. 



In 1888 in his memoir on the comatulids of the Challenger Expedition Carpenter 

 described Antedon flexilis in detail and figured it. Dr. Clemens Hartlaub in 1895 

 discussed the systematic and bathymetrical relationships of A. flexilis and compared 

 it with his new species Antedon (Tlialassometra) agassizii. Minckert in 1905 discussed 

 the syzygies of Antedon flexilis, and Hamann listed it in 1907. 



In my first revision of the genus Antedon published in 1907 flexilis was transferred 

 to the new genus Charitometra; it was again transferred to a new genus, Pachylometra, 

 in 1909. In the same year I published a correction of the dimensions given by Car- 

 penter in his original description, and in 1912 I compared it with a new species, Pachylo- 

 metra crassa. 



Hartlaub in 1912 mentioned Antedon flexilis in connection with his discussion of 

 the Spinifera Group, and in my memoir on the crinoids of the Indian Ocean published 

 in the same year I listed Pachylometra flexilis, giving the synonymy and locality. In 

 1913 I published a brief note on two of Carpenter's specimens which I had examined in 

 the British Museum. 



Upon the establishment of the new genus Perissometra in 1916 flexilis was trans- 

 ferred to it, and in my report on the unstalked crinoids of the Siboga Expedition pub- 

 lished in 1918 flexilis was included in the key to the species of Perissometra and the 

 synonymy and range were given. 



Prof. Torsten Gislen in 1928 published a note on the two specimens he had examined 

 in the British Museum. 



