132 DISCOVERY REPORTS 



CC Division series and brachials not as above; cirri of not more, usually much less, 

 than 40 segments ; P, about as long as Pj . 



D Pj of 28-40 segments; cirri of not more than 31 segments; lower brachials 

 with an abruptly elevated spinous patch in the distal portion of the dorsal 

 surface or with the distal edge everted at right angles and strongly pro- 

 duced ... ... ... ... ... ... ... Florometra mawsoni. 



DD Pj of more than 40 segments; lower brachials smooth or, exceptionally, 

 elevated into small and low spinous patches. 



E Pj of about 60 segments; cirri of 25-40 segments; lower brachials 

 smooth; brachials beyond third syzygy all short, much broader than 

 long ... ... ... ... ... ... ... Solanometra antarctica. 



EE Pj of 44-50 segments; cirri of 23-32 segments; lower brachials may 

 have small spinous patches; brachials beyond third syzygy not much 

 broader than long ... ... ... ... ... Florometra antarctica. 



AA Pj of less than 20 segments, usually short. 



B Third and some of succeeding segments of genital pinnules strongly expanded to 

 cover the gonads; oral pinnules short with their basal segments attached to the disk 

 or to the arm by webs of tissue. 



C Pg shorter than Pj . 



D Ventral surface of disk plated; P3 is first genital pinnule Isometra flavescens. 



DD Ventral surface of disk naked; P4-P6, usually Pg, first genital pinnule 



Isometra vivipara. 

 CC Pg as long as or longer than Pj. 



D Longest cirri of up to 70 segments; large robust species Isometra hordea. 



DD Cirri of 28-43 segments; fragile species of medium size Isometra graminea. 



BB No segments of genital pinnules strongly expanded. 



C Gonads not on pinnules but in axils between pinnules and arms; perisome 

 plated; oral pinnules short with their basal segments attached to the disk or to 

 the arms by webs of tissue. 

 D Cirri long, of 36-76 short segments of nearly uniform length Notocrirms virilis. 



DD Cirri shorter, of 21-32 segments of which some of the proximal are longer 



than the remainder ... ... ... ... ... Notocrinus mortenseni. 



CC Gonads in normal position on genital pinnules; perisome not plated; oral 

 pinnules (where present) entirely free. 

 D Pj and Pa absent ; P3 a genital pinnule ... ... Kempometra grisea. 



DD Oral pinnules present. 



E Cirri of less than 20 (12-19) segments. 



F First genital pinnule (Po or Pg) not much more than half as long 

 as Pj ... ... ... ... Phrixometra longipinna var. antarctica. 



FF First genital pinnule (Pg or P3) about as long as Pj . 



G Cirri about XLV ... ... ... Phrixometra nutrix. 



GG Cirri about XXX ... ... ... Phrixometra rayneri. 



EE Cirri of more than 20 segments (of up to 40 segments). 



F Cirri of 30-40 segments ... ... ... Eumorphometra fraseri. 



FF Cirri of less than 30 segments. 



G Cirri in 2 or 3 closely placed alternating rows; Pj longer and 

 more massive than Pg; in the lower genital pinnules the 

 segments carrying the gonad are slightly expanded 



Eumorphometra marn\ 



