c 1 cirri large, never slender, usually stout, tapering only very slightly, 

 if at all, distally ; distal cirrus segments shorter than the proximal, 

 broader than long, hearing prominent tubercles or spines dor- 

 sally; opposing spine long and well developed; terminal claw 

 stout, strongly curved (Maldive Islands and Ceylon to 

 northern Australia, and northward to southern 

 Japan) Amphimetra 



c 3 cirri small, very slender, nearly straight, tapering to a sharp 

 point ; distal cirrus segments proportionately as long as, or longer 

 than, the proximal, more than twice as long as broad, with no 

 dorsal processes ; no opposing spine ; terminal claw long, very 

 slender, and nearly straight (Arafura Sea; Moluccas) . . Homalometra 



Himerometra A. H. Clark. 



Key to the Species of the Genus Himerometra. 



a 1 Enlarged proximal pinnules slender, flagellate distally, and very long (slightly 

 more than one half the length of the cirri), composed of from 36 to 40 

 perfectly smooth segments most or all of which are longer than broad ; a 

 few of the earlier segments are narrowly, but prominently, carinate; the 

 earlier segments of the following pinnules are very strongly carinate; the 

 segments in the outer half of the cirri have prominent dorsal spines 

 b 1 20 to 25 arms; about 35 cirrus segments; all of the segments in 



the proximal pinnules are longer than broad (P e r s i a n G u 1 f ) . . persica 

 b" 35 to 61 arms; about 40 cirrus segments; a few of the basal segments 



in the proximal pinnules are broader than long (Philippin e Islands) bartschi 

 a' 2 Enlarged proximal pinnules very stout, with all or nearly all of the com- 

 ponent segments broader than long, or at least as broad as long; none of 

 the segments are carinate ; following pinnules without carinate processes 

 on the earlier segments 



b 1 enlarged proximal pinnules with about 30 segments, very stout basally 

 and distally gradually tapering to a delicate and flagellate tip ; the 

 distal edges of the segments in the middle half or proximal two-thirds 

 are swollen and may be strongly everted, but are always smooth, 

 never spinous 



c 1 cirri very stout, stouter than in any other species of the genus ; 

 the enlarged proximal pinnules have the segments in the basal 

 two-thirds with strongly produced and everted distal edges 



(Maldive Islands) sol 



ê cirri rather short and weak, without, or with only slight traces 

 of, dorsal processes on the outer segments ; the enlarged proximal 



SIBOGA-EXPEDITIE XLIli. IO 



