8 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



c 2 . No broadening or expansion of the genital pinnules, which are slender and evenly tapering. 



d 1 . PI and P a absent; cirri with 12-19 segments of which the second aiid third are about as 



long as broad and the fourth is longer than broad, but the distal are shorter; fifth-seventh 



or -eighth segments with a low curved transverse ridge, those following with a small 



simple dorsal tubercle; 10 arms 12-35 mm. long (southwestern Mindanao, Philippines, 



to the Bonin Islands; 72-80 meters) Clarkometra (p. 246) 



d 2 . PI always present, at least on the outer arms of a postradial series; P a may or may not be 



present. 



e 1 . Distal edges of the proximal cirrus segments fringed with spines; cirri with 29-65 seg- 

 ments of which the distal are shorter than the proximal, much broader than long, and 

 bear dorsally prominent paired, or rarely single, dorsal spines; one or more pairs of 

 the proximal pinnules elongated, much stiffened, and composed of elongated segments 

 with very spiny distal ends; segments of all the pinnules and the brachials with spiny 

 distal ends; 10 arms 40-170 mm. long (from the Philippine Islands and Singapore 

 southward to the Solomon Islands, Lord Howe Island, and Port Denison, Queensland, 



and westward to the Red Sea; 0-106 meters) Coloboxnetra (p. 116) 



e 2 . Distal edges of all the cirrus segments smooth. 



/'. Cirrus segments beyond the proximal fourth of the cirri with long median unpaired 

 dorsal spines; proximal pinnules short, P 2 the largest, with not more than 13 rather 

 short segments with spinous distal ends; cirri with 24-39 segments; 10 arms 20-80 

 mm. long (from the Philippine to the Kei and Andaman Islands; 80-113 meters). 



Cotylometra (p. 48) 



f 1 . Outer cirrus segments dorsally with a transverse ridge or paired tubercles or short 

 spines, sometimes with a median tubercle or spine on one or two before the penulti- 

 mate. 



g l . Cirrus segments with two dorsal transverse ridges, a proximal and a distal, appear- 

 ing in lateral view as two tubercles or short spines; P lf P 2 , and P 3 are enlarged and 

 stiffened, decreasing in length from P,, with 9-20 (usually 10-13) segments; the 

 cirri are XVI-XXXV (usually about XX), 17-32 (usually about 20); the 10 

 arms are 35-70 (usually about 50) mm. long (Aru Islands and northern Australia 

 south to Port Curtis, Queensland, and Cape Jaubert, Western Australia; 0-22 



[727] meters) Oligometrides (p. 61) 



g 1 . Cirrus segments dorsally with a single transverse ridge, or transverse row of tuber- 

 cles or spines, or paired spines, at least in the distal portion of the cirri. 

 h l . Cirrus segments dorsally with a low median keel and the distal edge slightly 

 thickened and produced, forming a distal transverse ridge; opposing spine 

 forked; P a absent throughout; PI usually absent on the inner arms of each 

 postradial series; PI, P 2 , and P 3 much elongated, exceedingly slender, with 

 greatly elongated segments, and stiffened; PI is shorter, less stout, and less 

 stiff than P 2 , with more numerous and shorter segments; Pj resembles P 2 , 

 but is of the same length as PI; about 40 arms about 50 mm. long (Philippine 



Islands; 106 meters) Epimetra (p. 25) 



h 2 . No median keel on the cirrus segments dorsally; opposing spine a simple spine or 



tubercle. 



f 1 . PI and P 2 , and sometimes also P a , are similar, elongated, stiffened, evenly 

 tapering, and of approximately the same length, composed of segments 

 which beyond the first two are much elongated. 



j 1 . PS much shorter, smaller, and weaker than P! and P 2 , which are similar and 

 of the same length; cirri with 19-31 segments which are subequal, about 

 twice as broad as long, sometimes slightly longer terminally; 10-31 arms 

 and 85-120 mm. long (from Flores to Amboina and Darwin, Australia, 

 and southward to Shark Bay, Western Australia; 0-40 meters). 



Petasometra (p. 105) 



i 1 . Pa resembles PI and P 2 and is abruptly different from the succeeding pin- 

 nules. 



