COPEPODS OF THE WOODS HOLE REGILN 583 



180. Head fused with first segment; urosome much longer than 



metasome; genital segment without dorsal suture; exopod of 

 second antenna 6-segmented; littoral, moderate depths. 



9 Sunaristes Hesse, 1867 

 Head separated from first segment; urosome shorter than 

 metasome; genital segment with dorsal suture; exopod 

 of second antenna 7-segmented 181 



181. Exopods of first 4 pairs of legs with inner setae; endopod of 



second antenna 2-segmented; caudal rami divergent; fifth 

 leg rudimentary, 4 setae; Httoral, among algae. 



& ? Canuella T. Scott, 1893 (p. 171) 

 Exopods of first 4 pairs of legs without inner setae; endopod of 

 second antenna 3-segmented; caudal rami parallel; fifth leg 

 lamellar, 5 setae; littoral, moderate depths. 9 Canuellina Gurney, 1927 



KEY TO THE GENERA OF THE SUBORDER CYCLOPOIDA 



(In addition to the segmentation of the swimming legs, the structure of the 

 second antennae and the fifth legs is of special systematic value.) 



1. Each ramus of the first 4 pairs of legs 3-segmented 2 



Each ramus of the first 4 pairs of legs 2-segmented 76 



Each ramus of the first 4 pairs of legs 1-segmented 81 



Rami of the first 4 pairs of legs unevenly segmented, or lacking 82 



2. Second antenna biramose, endopod 4-segmented, exoi:)od attached 



to outer side or distal corner of second endopod segment 3 



Second antenna uniramose, 5-segmented, the exopod lacking 21 



Second antenna uniramose, 4-segmented, the exopod lacking 23 



Second antenna uniramose, 3-segmented, the exopod lacking 59 



Second antenna uniramose, 2-segmented, the exopod lacking 71 



3. Urosome of female 3-segmented, of male 4-segmented 4 



Urosome of female 4-segmented, of male 5-segmented 12 



4. Outline of metasome circular or transversely elliptical, distinctly 



wider than long; oral cone short and ovate 5 



Outline of metasome oval or longitudinally elliptical, distinctly 



longer than wide; oral cone pear-shaped 6 



5. Metasome and genital segments without epimeral plates, dimin- 



ishing regularly in width; first antenna 18-segmented, fourth 

 segment without posterior spine; parasitic on starfish. 



9 Scottomyzon Giesbrecht, 1897 

 Metasome and genital segments with epimeral plates, second 

 and fourth segments abruptly narrowed; first antenna 17- 

 segmented, fourth segment with posterior spine; sponge 

 washings, Ceylon 9 Doropontius Thompson and Scott, 1903 



6. Second antenna as long as first, its exopod longer than third 



endopod segment, with 1 apical and 1 outer seta; oral tube 



reaching caudal rami; host unknown cf 9 Acontiophorus Brady, 1880 



Second antenna much shorter than first, its exopod shorter than 



third endopod segment; oral tube much shorter, sometimes lacking 7 



7. Oral cone not produced, sucking tube entirely lacking 8 



Oral cone produced into a sucking tube of moderate length 10 



8. Caudal rami 10 times as long as wide; end segment of fifth leg 



as wide as long, with 4 tiny setae; second antenna with 2 

 apical setae; dredged, 30 fathoms. 9 Mesocheres Norman and Scott, 1905 

 Caudal rami as wide as long or wider; end segment of fifth leg 



much longer than wide, with 3 apical setae 9 



