104 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



spines, at the same time moving to a position proximal to median. Here there may 

 be an eversion of the median part of the distal dorsal edge of the segments so that in 

 lateral view the segments may present more or less of the bidentate appearance 

 characteristic of Oligometrides adeonae. 



The 10 arms are about 18 mm. long. The division series and the arms in general 

 resemble those of Oligometra serripinna, but the elements of the IBr series and the first 

 brachials have broad and prominent ventrolateral processes as in the species of 

 Stephanometra. 



P is absent. P] is 2.5 mm. long with 8 segments and is the longest and stiffest 

 pinnule on the arm, though it is not especially stout. The first segment is half again 

 as broad as long, the second is about as long as broad, the third is twice as long as 

 broad, the fourth and fifth are between two and one-half and three times as long as 

 broad, and those following rapidly decrease in size. The third and following bear long 

 and prominent spines at the prismatic angles which after the fourth are very conspic- 

 uous. P 2 is 2 mm. long with 8 segments and exactly resembles P,. P 3 is small and 

 slender, about 1 mm. long with about 8 segments. The pinnules following are weak 

 and delicate, not tapering so rapidly as P 3 . 



Locality. Investigator; Andaman Islands [A. H. Clark, 1912, 1918; Gislen, 1919] 

 (1, I. M.). 



Remarks. The specimen upon which this species was based is obviously young, 

 and the absence of P a as well as the relatively large size of P! are very likely due simply 

 to immaturity. The form evidently belongs here, as is indicated by the characters of 

 the cirri, the broadening of the elements of the IBr series, and the similarity of the first 

 two pinnules, and not in Oligometra in which it was originally described, or in Deca- 

 metra (Prometra) in which it was subsequently placed. 



History. This species was described by me in 1912 under the name Oligometra 

 intermedia from a specimen collected by the Royal Indian Marine Surveying steamer 

 Investigator in the Andaman Islands. In my memoir on the crinoids of the Siboga 

 expedition published in 1918 I transferred it to the genus Prometra and included it in 

 the key to the species of that genus. 



In 1919 Dr. Torsten Gislen wrote that in such little species as intermedia one may 

 suspect that the absence of P a is due to youth and is not a mature character, as it is, 

 for instance, in Decametra. He left undecided the question whether intermedia is to 

 be considered as a real species or as a mere juvenile form of some larger species, pos- 

 sibly Oligometrides adeonae. 



UNIDENTIFIABLE SPECIES 

 [ANTEDON FIELDI Bell] 



Antedon fieldi BELL, Proc. Zool. Soc. London, 1894, p. 396 (listed), p. 401 (description; Macclesfield 

 Bank, 22-30 fathoms). HAMANN, Bronns Klassen und Ordnungen des Tier-Reichs, vol. 2, 

 Abt. 3, 1907, p. 1580 (listed). A. H. CLABK, Proc. U. S. Nat. Mus., vol. 34, 1908, p. 471 (un- 

 recognizable; certainly does not belong in the Spinifera group); Crinoids of the Indian Ocean, 

 1912, p. 38 (of Bell, 1894 = ?), p. 286 (original description quoted; remarks); Smithsonian Misc. 

 Coll., vol. 61, No. 15, 1913, p. 70 (original reference cited; Macclesfield Bank, 22-30 and 13 

 fathoms; appears to be a small species belonging to some genus of Mariametridae or Colobo- 

 metridae; strong transverse ridges on the cirrus segments). 



Remarks. Bell's description reads: "Allied to A[ntedon], moorei, but distinguished 

 from it by the broad spine [i. e., transverse ridge] on the cirrus joints. Cini about 20, 



