DISCUSSION OF SPECIES 



179 



2000 meters. This strongly suggests that the copepod is a 

 deep-water form which could be expected only rarely in the 

 upper 100 meters. 



Genus COPILIA Dana, 1849 



This genus is widely distributed in tropical and temperate 

 oceans, chiefly the former. All its species showed a preference 

 for the deeper levels, but denticulata was often, and quadrata 

 rarely, found at the surface. The species were also more or 

 less gregarious, occurring together at consecutive stations m 

 some localities, and entirely absent from the plankton in 

 others, often for long distances. 



Copilia denticulata Claus 



[CopiUa ihnticidata Claus, Die freilebenden Copepoden, p. 161, 

 pi. 25, 1863.] 



Found at eight Atlantic localities, and irregularly scattered 

 over the entire Pacific with large gaps in the southeastern and 

 northern parts. It was present in 3 nocturnal and 24 diurnal 

 surface tows, 48 50-meter tows, and 31 loo-meter tows. It was 

 thus found most frequently at the deeper levels in the day- 

 time, especially at the 50-meter level, but migrated to the 

 surface sometimes at night. 



Copilia mirabilis Dana 



[CopiUa mirabilis Dana, Proc. Amer. Acad. Arts and Sci., vol. 

 2, p. 40, 1849; U. S. Exploring E.xped., 1838-1842 (Wilkes), 

 vol. 14, pt. 2, Crustacea, p. 1232, 1853; pi. 86, fig. 14(7, b, 

 IS55-] 



Not present in the Atlantic plankton, but found at five 

 stations in the Pacific, one in the southeastern part and four 

 in the western part. At two of the stations the species was in 

 the 50-meter tow, at two others in the loo-meter tow, and 

 only once at the surface. In the Siboga plankton this species 

 was captured in 47 surface tows, 10 of which were nocturnal, 

 and in 8 vertical tows from considerable depths. As no simul- 

 taneous tows at different depths were taken on the Siboga 

 expedition, the most that can be said is that this copepod has 

 been taken so often at the surface in the daytime that it must 

 be at least indifferent if not positive to light. 



Copilia quadrata Dana 



[CopiUa quadrata Dana, Proc. Amer. Acad. Arts and Sci., vol. 

 2, p. 40, 1849; U. S. Exploring Exped., 1838-1842 (Wilkes), 

 vol. 14, pt. 2, Crustacea, p. 1233, 1853; pi. 86, fig. i^a-d, 

 1855-] 



Not present in the ,\tlantic plankton, but well scattered 

 over the Pacific, with large gaps in distribution in the south- 

 eastern and northern parts. It was taken in i nocturnal and 4 

 diurnal surface tows, 5 50-nieter tows, and 33 loo-meter tows. 

 Accordingly it was almost entirely confined to the two deeper 

 tows, especially the 100-meter tow, in the daytime, and must 

 be negative to light. During the Siboga expedition it was 

 taken in 21 surface tows, 6 of which were nocturnal. 



Copilia recta Giesbrecht 



[Copdia recta Giesbreclit, Atti R. Accad. Lincei, Rome, ser. 4, 

 vol. 7, sem. I, p. 480, i8gi; Fauna und Flora des Golfes von 

 Neapcl, vol. ig, pp. 648, 658, pi. 50, fig. 4, 1892.] 



This species was confined to four stations in the western 

 Pacific between the Mariana Islands and Japan, and was 

 present only in the two deeper tows, not appearing at the 

 surface. As far as is known, this copepod has been reported 

 only from the tropical Pacific and does not appear in any of 

 the lists of the larger plankton expeditions. 



Copilia vitrea (Hacckel) 



[Hyalopljyllum fitrcum Haeckel,'Ztschr. f. Med. u. Naturwiss., 

 Jena, vol. i, p. 63, pi. i, 1864. J 



Not present in the Atlantic plankton, but irregularly scat- 

 tered at many stations long distances apart in the Pacific. It 

 was found in 8 50-meter tows and 7 loo-meter tows, but did 

 not appear at the surface. Although not found in the Atlantic 

 during the present cruise, it has been reported from the 

 tropical Atlantic by Giesbrecht (1892, p. 647). 



Genus CORYCAEUS Dana, 1845 



The genus Corycaeus is confined to the temperate and 

 tropical regions and is rarely found above latitude 40° north 

 or below 40° south. It belongs, furthermore, to the epiplank- 

 ton, and the species are all found within the upper 100 

 meters. In spite of this, the vertical distribution of the various 

 species shows considerable diversity; see chart 6, on page 

 180. The names of the species are those given in the admirable 

 monograph on the Corycaeidae by Maria Dahl (1912), but 

 it has not been deemed necessary to include the subgenera. 



Corycaeus agilis Dana 



[Corycaeus agUis Dana, Proc. Amer. Acad. Arts and Sci., vol. 

 2, p. 37, 1849; U. S. Exploring Exped., 1838-1842 (Wilkes), 

 vol. 14, pt. 2, Crustacea, pp. 1217, 1218, 1853; pi. 85, fig. 

 I0i7, b, 1855.] 



Found at six localities in the Sargasso and Caribbean re- 

 gions, and irregularly scattered over the entire Pacific except 

 the north, but more abundant in the southeastern part. It was 

 taken in 44 surface tows, 17 50-meter tows, and 11 loo-meter 

 tows, and is thus a surface species, having a larger surface 

 predominance than any of the other species. 



Corycaeus andrewsi Farran 



(Figure 36) 



[Corycaeus andreivsi Farran, Proc. Zool. Soc. London, 1911, p. 

 294, pi. 13, figs. 7-9; pi. 14, figs. 1-4, 191 1.] 



This species was not present in the Atlantic plankton, and 

 in the Pacific was found chiefly in the southeastern part. It 

 was taken in 1 nocturnal and 5 diurnal surface tows, 3 50- 

 meter tows, and 6 loo-meter tows. Farran's (1911, p. 294) 

 original specimens were obtained in shallow water near the 

 shore of Christmas Island in the Indian Ocean, but other 

 specimens of both sexes were subsequently found by Maria 

 Dahl (1912, p. 78) in the western tropical Pacific. 



