'5i 



b 1 28 arms; stout and robust, with large stout cirri which are more than half 



the length of the arms (Lesser Sunda Islands; 204 Metres). . . magna 



\y 15 — 22 (usually 20) arms; slender, with slender cirri which are considerably 

 less than half the length of the arms (Malay Archipelago and the 

 Philippine Islands; 54 — 502 Metres) annandalei 



1. Oceanometra gigantea (A. H. Clark). 



A. H. CLARK. Proc. U.S. National Museum, vol. 34, 1908, p. 222 {Tlialassometra gigantea). 



2. Oceanometra magna (A. H. Clark). 



A. H. Clark. Zool. Anzeiger, vol. 39, 1912, N° u/12, p. 425 [Tlialassometra magna). 

 Stat. 251. 5°28'.4S., i32°o'.2E. Arafura Sea. 204 Metres. 1 Ex. 



The centrodorsal is conical, the sides slightly swollen, the tip truncated, 5.5 mm. broad 

 at the base and 5 mm. high; the dorsal pole is about 1.5 mm. in diameter, approximately 

 flat, covered with fine papillae; the cirrus sockets are arranged in ten columns, two to each 

 radial area, usually four (rarely three or five) to a column ; on the outer side of each radial 

 area the columns are closely crowded against the columns of adjacent radial areas, but in the 

 midradial line they are separated by a bare, slightly concave, area which proximally is nearly 

 or quite as broad as the adjacent cirrus sockets, but which rapidly becomes narrow so that 

 the outermost one or two sockets in each area are in contact in the midradial line. Very deep, 

 though very narrow, subradial clefts separate the centrodorsal from the radials. 



The cirri are XXX — XL, 66 — 74, 70 mm. to 85 min. long; the shorter cirri toward 

 the apex of the centrodorsal are 60 mm. long with 59 segments. The first cirrus segment is 

 very short, and the following slowly increase in length to the fifth, which is slightly more than 

 twice as broad as long, and the seventh, which is about as long as broad; the eighth is a 

 transition segment, nearly or quite twice as long as the distal diameter; the ninth is similar; 

 the following slowly decrease in length to the twenty-second or twenty-third, which is about as 

 long as its proximal diameter, and still further to those in the distal fifth of the cirri, which are 

 twice as broad as long, and the terminal, which are still shorter. On the fifteenth or sixteenth 

 the distal dorsal edge begins to project in the median line; on the succeeding segments this 

 projection slowly increases in extent and, the middorsal line of the segments rising into a sharp 

 keel, transforms on the short distal segments into the very high carinate dorsal spines charact- 

 eristic of the genus. The last six or seven segments gradually decrease in diameter so that 

 the penultimate segment is very small. The distal edges of the earlier segments, especially 

 dorsally, are very finely spinous so that the cirri are rough to the touch. 



The ends of the basal rays are visible as dorsoventrally elongate tubercles bridging over 

 the subradial clefts. 



The radials are very short, with a slight rounded median prominence and with a few 

 small teeth on the distal margin. The IBr x are short, between four and five times as broad as 



