A MONOGRAPH OF THE EXISTING CRINOIDS 543 



flexible throughout; it tapers rapidly on the first six segments, then becoming slender 

 and flagellate. P 2 is 21 mm. long with 32 segments; it is very slightly larger basally 

 than P! but tapers much more gradually, becoming flagellate only in the distal third ; 

 it is somewhat stiffened in the proximal two-thirds but flexible in the distal third. 

 P 3 is 24 mm. long with 30+ segments (the tip is broken), which become about as long 

 as broad on the fifth and nearly twice as long as broad in the distal third ; it is about as 

 large basally as P 2 but tapers gradually to the tip; it is somewhat stiffened throughout. 



Another specimen has also 40 arms. 



A third specimen has 39 arms about 130 mm. long. The cirri have 28-30 seg- 

 ments, of which the longest are slightly longer than broad and the distal are nearly 

 twice as broad as long with small but conspicuous dorsal spines that begin at, or more 

 or less beyond, the middle of the cirri. P 3 is the largest and longest pinnule on the 

 arm but is not greatly larger or longer than P 2 . P 4 is about like P 2 . 



A fourth specimen has 37 arms about 215 mm. long. The cirri are XXX, 28-31, 

 moderately stout, uniform in size, with the longest segments about as long as broad 

 and the segments in the distal third with a low carinate dorsal spine. P! is 8 mm. long 

 with about 20 segments. P 2 is about twice as long as P,. P 3 is about 25 mm. long, 

 with 36 segments, and is much the longest and largest pinnule, though it is not espe- 

 cially enlarged and is very flexible. 



Localities. Amboina; coll. Ludeking [P. H. Carpenter, 1881, 1883, 1888; Bell, 

 1882; Hartlaub, 1891; A. H. Clark, 1907, 1909, 1911, 1912, 1913, 1918] (1, L. M.). 



Port Galera, Mindoro, Philippines; Dr. Lawrence E. Griffin [color described in 

 part 2, p. 717] (7, M. C. Z., 632, 701, 702). 



Geographical range. From Amboina to Mindoro, Philippines. 



Bathymetrical range. Littoral. 



History. Dr. P. H. Carpenter first described this species in 1881 under the name 

 of Antedon bimaculata from a specimen in the Leyden Museum that had been collected 

 by Ludeking at Amboina. In the following year Prof. F. J. Bell proposed a specific 

 formula for it, which was emended by Carpenter early in 1883. 



In the Challenger report on the comatulids published in 1888 Carpenter inserted 

 bimaculata in his key to the species of the Palmata group, in which it was grouped with 

 elongata (^flagellata) and fiagellata under the heading P 3 larger than P 2 . Its differ- 

 ential characters were given as "Cirri not spiny; second syzygy about the twentieth 

 brachial," the other two forms being grouped under the heading ''Spiny cirri." 



Dr. Clemens Hartlaub in 1891 placed bimaculata in his key to the species of the 

 Palmata group, repeating the differential characters employed by Carpenter. 



In my first revision of the old genus Antedon published in 1907, bimaculata was 

 transferred to the new genus Himerometra, and in a revision of the family Himerometri- 

 dae published in 1909 it was placed in the new genus Dichrometra. 



In my paper on the comatulids of the Leyden Museum published in 1911, the 

 type specimen of Antedon bimaculata, which I had examined in 1910, was redescribed. 



Dichrometra bimaculata was listed in my memoir on the crmoids of the Indian 

 Ocean published in 1912 and was included in the key to the species of Dichrometra in 

 my report upon the unstalked crinoids of the Siboga expedition published in 1918. 



