198 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



lAmphimetra sinensis A. H. CLARK, Proc. Biol. Soc. Washington, vol. 26, 1913, p. 179 (range in 

 east Asia); Journ. Washington Acad. Sei., vol. 5, No. 6, 1915, p. 214 (Malayan species; range 

 and its significance); Uustalked crinoids of the Siboga-Exped., 1918, p. 90 (references; notes; 

 identity doubtful). 



Decametra laevipinna A. H. CLARK, Unstalked crinoids of the Siboga-Exped., 1918, p. viii (discovery 

 by the Siboga and its significance), p. 118 (in key; range), p. 120 (detailed description; station 

 213). p. 274 (listed), pi. 20, figs. 42, 43; Temminckia, vol. 1, 1936, p. 295 (listed), p. 308 (Obi 

 latoe, Sipankot; Boo Islands; notes), pi. 8, fig. 7. 



Diagnostic jeatures. The cirri are 10-15 mm. long with 18-25 (usually 23-25) 

 segments mostly about as long as broad, all but the basal with a transverse ridge 

 dorsally; P 2 is 6.5-7.8 mm. long, longer than P,, with 17-19 segments and perfectly 

 smooth; P 3 is similar to P 2 with an equal number of, or fewer, segments, but shorter; 

 the arms are 40-50+ mm. long. 



Description. The centrodorsal is discoidal with a broad, flat, circular dorsal 

 pole 2 mm. in diameter. The cirrus sockets are arranged in a single closely crowded 

 marginal row. 



The cirri are XIV, 18-23, 13 mm. long. The first segment is very short, those 

 following gradually increasing in length and after the tenth or eleventh being about 

 as long as broad. The first segment has the distal dorsal edge produced; on the 

 second and third this production becomes a strong transverse ridge that gradually 

 moves anteriorly, becoming median on the eighth and following where it appears as 

 a minute median spine in lateral view. This ridge shows no tendency to resolve 

 itself into paired spines or tubercles, nor does it narrow appreciably on the outer 

 segments, occurring as a broad transverse ridge even on the antepenultimate. The 

 opposing spine is small, slender, median, and erect, in height about equal to one-fourth 

 the width of the penultimate segment. 



The arms resemble those of the other species of the genus, and are about 50 mm. 

 long. 



PI is 5.5 mm. long, moderately slender, somewhat stiffened, with 14 or 15 segments 

 of which the first is short and those following gradually increase in length becoming 

 about as long as broad on the fifth and on the outer very slightly longer than broad; 

 from the third segment outward the pinnule is rather strongly prismatic with a 

 prominent rounded ridge running along the center of the outer surface. P 2 is 6.5 

 mm. long with 17 segments, resembling PI but slightly more slender basally and taper- 

 ing more evenly to the tip, and not so strongly prismatic; the distal edges of the 

 segments of both these pinnules are perfectly smooth. P 3 is 4.5 mm. long with 14 

 segments, similar to P 2 but proportionately smaller and more slender distally. P 4 

 is 3.5 mm. long with 13 segments, small and slender. P 6 is similar, 3 mm. long, 

 with 11 segments. P a is similar to P 6 , 3 mm. long with 12 segments. The distal 

 pinnules are very slender, 7 mm. long with 20-22 segments. 



Notes. The specimen from Hong Kong probably representing this species was 

 thus described by Hartlaub: 



The centrodorsal is flat discoidal with marginal cirri. The cirri are about XVI, 

 about 25, about 10 mm. long, and rather slender. The cirrus segments are very 

 uniformly short. In the distal half of the cirri the distal ends of the segments dor- 

 sally are somewhat produced so that the cirri here have a bluntly serrate dorsal 

 profile. The opposing spine is well developed. The radials are scarcely visible. 



