32 THE VOYAGE OF H.M.S. CHALLENGER. 



in the male, the twenty-five jointed anterior antennae, together with the characters 

 of the posterior antennae and mouth-organs, are the characters upon which rest the 

 claims of Calanus to generic rank. The species are probably very numerous, and are 

 found near the surface of the sea in all parts of the world. In some species, though 

 perhaps not in all, there is a remarkable difference between the posterior foot-jaws of 

 male and female, those of the male being somewhat smaller, stouter, and armed on the 

 outer margin, near the apex, with two or more stout and profusely plumose recurved setae. 



1. Calanus finmarchicus (Gunner) (PI. I. figs. 1-10). 



Monoeulus finmarchicus, Gunner, Act. Hafn. x., 175, figs. 20-23 (1765). 



Cetochilus septentrionalis, Goodsir, Edin. New Phil. Journ. 35, p. 339, t. vi. figs. 1-11 (1843). 



,, „ Baird, Nat. Hist. Brit. Entom., p. 235, t. xxx., figs. 1 a-g (1850). 



„ helgolandicus, Claus, Die frei lebenden Copepoden, p. 171, t. xxvi., figs. 2-9 (18G3). 

 Calanus finmarchicus, Boeck, Oversigt over de ved Norges Kyster iagttagne Copepoder, 



p. 8 (18G4), Brady, Monogr. of the Copepoda of the British Islands, vol. i. p. 38, pi. i. 



figs. 1-12 (1878). 

 Calanus magnus, borealis and elegans, Lubbock, Ann. Hag. Nat. Hist., ser. 2, vol. xiv. (1854). 



Length, l-7th of an inch (3 "5 mm.). 1 Forehead broadly rounded, rostrum long, slender 

 and bifid, anterior antennae twenty-five jointed, as long as the body, each joint bearing- 

 two or three short setae (except those near the base in the female), the twenty-third and 

 twenty- fourth joints each with a long apical seta ; most of the joints of the male 

 antenna (fig. 1) are constricted at the point of articulation, and bear fusiform or club- 

 shaped appendages at the apices. The branches of the posterior antenna? (fig. 3) arc 

 stout and nearly equal ; those of the mandible-palp (fig. 4) are short and nearly equal, 

 one indistinctly four-jointed, the other two-jointed, with the first joint much swollen. 

 The swimming feet are long and slender, terminal spines slender and without serratures 

 (fig. 9), the first joint of the peduncle of the fifth pair, in both sexes, has its inner margin 

 bordered with about fifteen sharp teeth of equal size throughout ; the outer branch of 

 the right side, in the male, has its first two joints much elongated (fig. 10), equalling in 

 length the three joints of the left limb ; the last joint is much shorter, ovate, and bears 

 three or four small slender setae near its apex. The mouth is provided with two very 

 strongly toothed lips (fig. 5). 



Habitat. — Taken in the tow-net, off Cape Howe, Australia, at night, and in lat. 

 36° 32' S., long. 132° 52' W. (Station 287). 



In my preliminary notes and drawings of these Australian specimens, I set the species 

 down as undescribed, relying upon the marked moniliform character of the anterior male 

 antennae, and the peculiar reflexed seta? of the posterior foot-jaw in the same sex. But 

 further examination of northern specimens has showed me that both those characters, not 



1 The measurements are always exclusive of the tail setae. 



