358 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



plates that generally mark the ambulacra are barely distinguishable. He also said 

 that the fertile intrapinnular portion of the genital gland is short, thick, and rounded, 

 and extends only over four or five of the pinnule segments. 



In London I examined six specimens of Carpenter's type series and remarked that 

 the constriction of the lower portion of the calyx seems to be a valid character for 

 differentiating this species from P. scalaris. 



The specimens from Siboga stations 122 and 124 resemble each other and do not 

 seem to differ appreciably, in size or otherwise, from others at hand dredged by the 

 Challenger. In young individuals in which the radials are still about half as large as 

 the IBi'i there is but little trace of the dorsolateral processes characteristic of the adults; 

 they are only slightly evident, though they can be made out as a thickened ridge in the 

 place they will eventually occupy. At this stage also the genital pinnules are slender and 

 evenly tapering, showing no trace of the lateral expansion of the segments which is so 

 marked a feature in the fully grown. As the radials become shorter the proximal border 

 of the IBr! becomes produced so that it conceals the radials and the proximal edge of 

 the centrodorsal when the animal is viewed laterally. The dorsal surface of the radials 

 is gradually resorbed as the proximal margin of the IBr! is produced, so that the IBr 

 series and arms appear to be too large for the radials and the centrodorsal, giving the 

 appearance of having been glued upon them rather than of having grown out from 

 them. In very large specimens the produced proximal and lateral borders of the IBr,, 

 which are typically smooth, become crenulate and scalloped. 



Localities.— Challenger station 214; off the Meangis Islands (lat. 4°33' N., long. 

 127°06' E.); 914 meters; bottom temperature 5.44° C; blue mud; February 10, 1875 

 [P. H. Carpenter, 1880, 1884, 1887, 1888; Hartlaub, 1891; Shipley and MacBride, 

 1901; Minckert, 1905; Hamann, 1907; A. H. Clark, 1907, 1909, 1912, 1913, 1918; 

 Gislen, 1924] (9, USNM, 35659; M. C. Z., 296, 606; B. M.). 



Siboga station 124; northeast of the northeastern tip of Celebes (lat, 2°27' N., 

 long. 125°35' E.); 1,327 meters; stone; July 18, 1899 [A. H. Clark, 1918] (2, Amsterdam 



Mus.). 



Siboga station 122; north of the northeastern tip of Celebes (lat. 1°58'30" N., 

 long. 125°00'30" E.); 1,165-1,264 meters; stone; July 17, 1899 [A. H. Clark, 1918] (7, 

 Amsterdam Mus.). 



Geographical range. — Between northern Celebes and Mindanao, Philippines. 



Bathymetrical range. — From 914 to 1,327 meters. 



Thermal range. — One record, 5.44° C. 



History.— In a popular article published in 18S0 Dr. P. Herbert Carpenter gave a 

 figure of part of a distal pinnule of a comatulid he identified only as "a new species of 

 Antedon from the Pacific" showing the side and covering plates. In his memoir on the 

 talked crinoids of the Challenger Expedition published in 1S84 he mentioned Antedon 

 acoela several times, giving a specific formula (page 57, footnote 4) and discussing the 

 peculiarities of the genital pinnules and the disk. He included a figure of the ventral 

 view of part of an arm showing live genital pinnules, and also a lateral and ventral view 

 of a single genital pinnule. He republished the figure of part of a distal pinnule given 

 in 1SS0 lengthened so as to show four and a half pinnule segments instead of three, and 

 thirteen side-plates instead of nine. In a paper published in 1887 Carpenter discussed 

 the sacculi of Antedon acoela and republished the figure of a portion of the distal pinnule. 



