346 SMITHSONIAN MISCELLANEOUS COLLECTIONS [ V °L- 5° 



distally; centro-dorsal cliscoidal with numerous cirri, 

 which are composed of greatly elongated smooth 

 joints; terminal claw very long and nearly straight; 

 no opposing spine; middle and distal arm joints dis- 



coidal ; brown or grayish (5) Thysanometra 



ccc. One or more of the lower pinnules elongated ; but all the 

 lower pinnules are slender and have elongated, 

 smooth, cylindrical joints. 

 d. The first joint of the elongated proximal pinnules is always 

 short ; distal pinnules cylindrical, very slender, not 

 elongated; centro-dorsal hemispherical or discoidal, 

 the cirri without definite arrangement; some or all 

 of the cirrus segments markedly "dice-box shaped." 

 (6) Ante don de Freminville 

 dd. All the pinnules greatly elongated, the first joint as well 

 as the others very long; centro-dorsal conical or long 

 columnar, divided by five broad interradial ridges or 

 planes into areas, each with definite vertical rows of 

 cirrus sockets ; cirrus segments cylindrical or flat- 

 tened, never "dice-box shaped." 

 e. Costals and lower brachials smooth, well-separated, and 

 rounded; cirri smooth with all the joints elongated, 

 arranged in 3, 4 or 5 rows in each radial area. 



(7) Psathyrometra 



ee. Costals and lower brachials spiny, sharply "wall-sided ;" 



cirri with much elongated joints proximally, very 



short and spiny joints distally, arranged in 2 rows in 



each radial area (8) Zenometra 



cccc. Lower pinnules cylindrical, one or more enlarged, very stout, 

 styliform, or more or less flagellate. 

 d. Cirri without definite arrangement ; centro-dorsal discoidal. 

 e. Cirri long with 50-70 short segments, bearing dorsal 

 spines distally; pinnule of second brachial greatly 

 elongated and flagellate, the following pinnules very 

 short ; costals widely free laterally, and rounded. 



(9) Pontiometra 

 ee. Cirri moderate or short, with not more than 40 seg- 

 ments ; one or more of the lower pinnules very stout, 

 stiff, elongate, styliform or more or less flagellate, 

 with cylindrical segments ; following pinnules de- 

 crease gradually in length ; outer surface of costals 

 (also distichals and palmars when present) and lower 

 brachials rounded, never carinate, convex dorso- 

 ventrally, imparting a swollen appearance to the seg- 

 ments, usually more or less tubercular. 



(10) Himerometra 

 dd. Cirri in 10 vertical rows, on a long conical centro-dorsal. 



(18) Adelometra 

 bb. No pinnule on the 4th (epizygal) brachial. 



c. Centro-dorsal discoidal, the short cirri in two or three irregular 

 marginal rows ; costals and lower brachials not 



