smaller than on female; setae of lobe-5 nude; large 

 setae distal from lobe-5 wider and more coarsely 

 spinulose than on female, especially 1 of terminal 3 

 setae and largest seta of lobe-6. No spines on lobe-5 

 base; no outer seta observed. 



Mxp (Fig. 30) somewhat reduced; several setae of 

 reduced size, especially on Bl-2 and outer edge of Ri4- 

 5. but number as on female. Bl surfaces nude. B2 

 relatively thinner than on female, with longitudinal 

 row of stiff hairs. Ri5 inner edge without spinules. 



Pi similar to female PI except Re outer spines 

 wider, shorter, and smoother. Ri outer lobe rounded. 



P2 similar to female P2 except Bl outer surface 

 with long thin setules, and Re outer spines longer than 

 on female. 



P4 (Fig. 31) Bl nude; Ri as on female, except more 

 spines in each row. Re2 posterior surface with row of 

 ca. 8 leatlike spines followed distally by more or less 

 circular patch of ca. 15 small spines; Re3 with ca. 17 

 denticles in 3 groups on posterior surface; serrations 

 on terminal seta finer than on female, ca. 50 primary 

 teeth. 



P5 (Figs. 32, 33) reaching to end of urosome seg- 

 ment 2; biramus, left-handed. Left Bl reaching mid- 

 dle of right B2; left B2 reaching two-thirds length of 

 right Rel. Left leg longest; left Re, including terminal 

 blade, longest; right Ri not much longer than left. 

 Order of length, longest to shortest, of Re segments: 

 left 2, 1, 3; right 1 = 2 = 3. Left Ri reaching one-third 

 length of left Re2; right Ri reaching to right Re3. 

 Probably each Rel with short, flat seta on outer distal 

 edge (not seen on Arctic specimens). Right Rel-2 

 more or less fused. Inner edge of left Rel-2 with long 

 hairs. Each Re with 1 small and 1 moderate bladelike 

 terminal setae. 



Male stage V.— Length 0.88-0.95 mm. P5 (Fig. 34) 

 biramus, symmetrical. Re 1-segmented with trace of 

 segmentation about one-third length; 2 unequal ter- 

 minal setae. Ri 1-segmented, thin distal portion 

 reaching about two-thirds length of Re. 



Remarks 



Sars (1900) did not describe the well-developed 

 spines on the posterior surface of P2-P4 Re, even 

 though the material he examined is as described 

 above. Sars mistakenly illustrated an outer seta on P2 

 Ri2; his slide (OSLO F6511) only has 1 P2, which was 

 mounted so that the inner seta of Rel met the Ri at 

 the base of a surface spine, giving the appearance of a 

 fifth seta on Ri2. Sars' slide was remounted and it was 

 seen that there is no outer seta on P2 Ri2 of the 

 holotype or on any other S. longicornis studied. 



Sars' (1900) description of a male S. longicornis was 

 pointed out first by Mrazek (1902) not to be of the 

 male, and later Sars (1903, p. 157) confirmed that it 

 was a Microcalanus species. A vial from the 

 Norwegian North Polar Expedition (F2482) labeled by 



Sars "Spinocalanus longicornis" contained only one 

 male Microcalanus species; sample 15 (Table 3) also 

 contained, in addition to S. longicornis, one male, one 

 male stage V, and two female Microcalanus species. 



Mrazek (1902) repeated Sars' record oi S. longicor- 

 nis. Mrazek also described the male and female of a 

 new species, S. schaudinni, which is considered here 

 as conspecific with S. longicornis. Mrazek's descrip- 

 tion provided much of what Sars' lacked, and led 

 Mrazek to believe that the two species were distinct. 



Brodsky (1950) was the first to state that S. 

 longicornis was probably equivalent to S. schaudinni, 

 and at the same time distinct from both S. abyssalis 

 Giesbrecht and S. longicornis/ S. abyssalis. — Sars, 

 1901, 1903 (see S. brevicaudatus) . Brodsky reported 

 that the outer spines on PI Re do not reach the base of 

 the following spines; specimens in the present study 

 had longer spines, and this feature is considered 

 variable. 



Farran's (1926) S. abyssalis var. pygmaeus has been 

 assumed by Park (1970) and Grice (1971) to be 

 equivalent to S. abyssalis Giesbrecht. Some of 

 Farran's specimens were examined in the present 

 study (sample 1, Table 3) and were determined to be 

 S. longicornis. It is possible, however, that Farran in- 

 cluded both species in this variety, since they co-occur 

 in the North Atlantic. 



Park's (1970) S. parabyssalis holotype was deter- 

 mined to be S. longicornis; Park's description and 

 figures of the female are consistent with the above 

 description of S. longicornis. The male S. 

 parabyssalis, however, is believed to be S. abyssalis. 



Grice's (1971) figures of S. parabyssalis also agree 

 with the description of S. longicornis. The references 

 to these figures are correct in his key, but the figure 

 legend transposed the caption for S. abyssalis and S. 

 parabyssalis (G. Grice, pers. commun.). 



Of the material examined in the present study, the 

 suture between Th4 and Th5 was clear on most of the 

 Arctic S. longicornis females, and on the two females 

 from sample 1. These segments were partly fused on 

 the S. parabyssalis holotype, from sample 55, and on 

 the six females from sample 23. 



Mxp B2 spine-comb was present right and left on 

 the specimens in sample 1, and on 4 Arctic specimens; 

 on left but not right on 2 Arctic specimens; absent on 

 the holotype from sample 15, the 6 females from sam- 

 ple 23, and 12 other Arctic specimens. 



Distribution 



Some records of S. abyssalis or S. abyssalis var. 

 pygmaeus may be based on either or both S. abyssalis 

 and S. longicornis (see discussion under S. abyssalis); 

 these include specimens as short as 0.8-0.83 mm. 



Probable or confirmed occurrences of S. longicornis 

 are summarized below. Bogorov (1946a) recognized 

 two species, based primarily on size, S. longicornis 

 and S. abyssalis; presumably the latter was the larger 

 (see S. elongatus). Bogorov identified the material 



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