582 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



MABIAMETRA TENUIPES A. H. Clark 



PLATE 61, FIGURE 282 



Mariametra tenuipes A. H. CLARK, Ann. Mag. Nat. Hist., ser. 8, vol. 10, 1912, p. 32 (description; 

 Siboga station 294); Proc. Biol. Soc. Washington, vol. 26, 1913, p. 144 (listed); Unstalked 

 crinoids of the Siboga-Exped., 1918, p. vin (discovery by the Siboga and its significance), p. 108 

 Gn key; range), p. 110 (detailed description; station 294), p. 275 (listed), pi. 20, fig. 47. GISL^N, 

 Kungl. Fysiogr. Sallsk. Handl., vol. 45, No. 11, 1934, p. 20. 



Mariametra tenuicirra A. H. CLARK, Unstalked crinoids of the Sifcoja-Exped., 1918, p. vm (editorial 

 error) . 



Diagnostic features. The arms are 15 in number, about 45 mm. long; the division 

 series and arms have a median line of dark purple; the sides of the ossicles of the 

 division series bear irregular and closely crowded short blunt spines; the cirri, which 

 are approximately half as long as the arms, have 24-29 segments, of which the longest 

 are about three times as long as the median width and the last 10 or 11 are about as 

 long as the distal width or very slightly longer; the eleventh and following segments 

 have slight subterminal dorsal spines; P 3 is 11 mm. long, with 21 segments, and is less 

 than half again as long as P 2 . 



Description. The dorsal pole of the centrodorsal is slightly convex, 1 mm. 

 in diameter, and is covered with small tubercles. 



The cirri are XXVI, 24-29, 22 mm. long. The first segment is short, the second 

 is about twice as broad as the median length, the third varies from slightly longer 

 than broad to half again as long as broad, and the sixth-eighth are about three times 

 as long as the median width. The segments following gradually decrease in length 

 so that the last 10 or 11 are about as long as their distal width or only very slightly 

 longer. The cirri are exceedingly slender. The long proximal segments have slightly 

 prominent ends. Slight subterminal dorsal spines appear on about the eleventh 

 segment. 



The division series and arms resemble in general those of the other species of the 

 genus. One IIIBr series is present, externally developed. The lateral ornamentation 

 of the division series, which occupies the outer thirds of the exposed surface of the 

 elements of the IBr series, thence narrowing distally and disappearing at the base of 

 PI, consists of very numerous small blunt spines, more or less coalescent, that show a 

 tendency to become arranged in horizontal rows. 



The 15 arms are probably about 45 mm. long. 



PI is small and short, 6 mm. long, with about 16 segments. P 2 is 7.5 mm. long, 

 with 19 segments, resembling P 3 but not so stout, though slightly stouter than PI. 

 P 3 is 11 mm. long, with 21 segments, and is slender and evenly tapering. The first 

 segment is not quite so long as broad, the second is about as long as broad, and the 

 fifth and following are about twice as long as broad, becoming more elongated termi- 

 nally. P 4 is 9 mm. long, with 19 segments, and resembles P 8 . 



Locality. Siboga station 294; off Timor (lat. 1012'12" S., long. 12427'18" E.); 

 73 meters; soft mud with very fine sand; January 23, 1899 [A. H. Clark, 1912, 1913, 

 1918] (1, Amsterdam Mus.). 



History. Mariametra tenuipes was described in 1912 from a single specimen 

 dredged by the Siboga at station 294; it was redescribed and figured in 1918. The 

 type specimen still remains unique. 



