face of some segments in female sometimes circular 

 clusters in male. P4 Bl without inner transverse row 

 of setules or spinules on posterior surface; with or 

 without inner seta. 



P5 biramus or very asymmetrical uniramus, usually 

 left-handed (S. polaris and S. similis right-handed); 

 each Re essentially 3-segmented, usually right Rel 

 and Re2 more or less fused on left-handed species. 



Key to the Species of Spinocalanus 



GROUP A. PI Ri with 2 inner setae; P2 Ri2 

 with 0-1 outer seta; P3-P4 Ri3 with 2 outer setae. 

 A2 Rel with 1-2 setae. Female: Th5 lateral cor- 

 ners prolonged or not; Thl-Th4 with or without 

 lateral spinules. Mxp Bl with 0, 1, or 3 transverse 

 spine-combs; B2 generally with transverse spine- 

 comb, 2 species variable, 1 species without; Ri4-5 

 outer 2 setae fragile, bladelike, nude, tapered 

 toward each end; Ri5 inner edge with 

 spinules. Male: Anal segment reduced. Al seg- 

 ment 25 reduced. Mxp Ri4-5 outer 2 setae reduced, 

 may be bladelike as in female; inner setae of Ri2-5 

 not inflated; Ri5 inner edge with or without 

 spinules. P5 biramus, left- or right-handed (14 

 species) (1) 



GROUP B. PI Ri with 3 inner setae; P2 Ri2 

 with 1 outer seta; P3-P4 Ri3 with 2 outer setae. A2 

 Rel without setae. Female: Th5 lateral corners 

 prolonged; Thl-Th4 without lateral spinules. Mxp 

 Bl-2 without transverse spine-combs; Ri4-5 outer 2 

 setae may be asymmetrically plumose and as large 

 and strong as other large terminal setae, or lightly 

 plumose, moderately fragile, thin, and relatively 

 short; Ri.5 inner edge without spinules. Male: 

 Anal segment not reduced. Al segment 25 not 

 reduced. Mxp Ri4-5 outer 2 setae reduced; inner 

 setae of Ri2-5 not inflated; Ri5 inner edge without 

 spinules. P5 left-handed; uniramus and very 

 asymmetrical, or biramus (4 species) (17) 



GROUP C. PI Ri with 1 inner seta; P2 Ri2 with 

 no outer seta; P3-P4 Ri3 with 1 outer seta. A2 Rel 

 with 1 seta. Female: Th5 lateral corners 

 prolonged; Thl-Th4 without lateral spinules. Mxp 

 Bl-2 without transverse spine-combs; Ri4-5 outer 2 

 setae lightly plumose, moderately fragile, thin, and 

 relatively short; Ri5 inner edge without 

 spinules. Male: Anal segment reduced. Al seg- 

 ment 25 reduced. Mxp Ri4-5 outer 2 setae reduced 

 or absent; inner setae of Ri2-5 inflated; Ri5 inner 

 edge without spinules. P5 biramus, right-handed (1 

 species) 26. S. polaris 



1. P2 Ri2 with 1 outer seta. A2 Rel with 2 setae. 

 Female Thl-Th4 with or without lateral 

 spinules (10 species) (5) 



P2 Ri2 with no outer seta. A2 Rel with 1 seta. 

 Thl-Th4 without lateral spinules (4 spe- 

 cies) (2) 



2. P3-P4 Re2 proximal posterior surface spines 



broad, leaflike. Female: Th5 rounded, 

 not prolonged. Mxp Bl without transverse 

 spine-comb. Male: P5 longest Ri about 

 equal to or less than II2 times length of 



other Ri . . (4) 



P3-P4 Re2 proximal posterior surface spines 

 relatively narrow, not leaflike. Female: 

 Th5 slightly prolonged. Mxp Bl with 1 or 3 

 transverse spine-combs. Male: P5 long- 

 est Ri more than 1'2 times length of other 

 Ri (3) 



3. Female: Al terminal 2 segments elongate. 



Mxp Bl with 3 transverse spine-combs; Ri3 

 with 2 setae. Male: Left-handed . . . 



25. S. elongatus 



Female: Al terminal 2 segments of moderate 

 length and width. Mxp Bl with 1 transverse 

 spine-comb; Ri3 with 3 setae. Male: 

 Right-handed 21. S. similis 



4. Female: Prosome, slender ovoid, length great- 



er than 2.4 times width. Male: P5 Ri 

 lengths very unequal .... I. S. abyssalis 

 Female: Prosome, somewhat robust ovoid, 

 length less than 2.4 times width. Male: 

 P5 Ri lengths about equal .... 2. S. longicornis 



5. Female (8) 



Male (unknown for 7 of 10 species) .... (6) 



6. P5 Ri not reaching base of Re3 terminal 



setae 10. S. horridus 



P5 Ri reaching beyond base of Re3 terminal 

 setae (7) 



7. PI Re3 posterior surface without spines . . 



27. S. brevicaudatus 



Pi Re3 posterior surface with spines .... 

 43. S. terranovae, new species 



8. Th5 lateral corners rounded (10) 



Th5 lateral corners more or less prolonged, not 



rounded (9) 



9. Length less than 2 mm. Mxp B2 without 



transverse spine-comb. P1-P4 Bl surfaces 

 without dense covering of fine hairs. (Male 



unknown.) 31. S. abruptus 



Length greater than 2 mm. Mxp B2 with 

 transverse spine-comb(?). P1-P4 Bl sur- 

 faces with dense covering of fine hairs. 

 (Male unknown.) 8. -S. hirtus 



10. At least 1 segment Thl-Th4, right and/or left, 



with ventrolateral spinules (13) 



Thl-Th4 without spinules (11) 



11. Mxp Bl with transverse spine-comb. (Male 



unknown.) 39. S. aspinosus 



Mxp Bl without transverse spine-comb . (12) 



12. PI Re3 posterior surface without spines. P2 Bl 



surface without spines (spinules and/or 

 setules only). P3 Re2 posterior surface with 

 row of spines distal from row of strong 



16 



