196 



COPEPODS OF LAST CRUISE OF CARNEGIE 



Oithona attenuata Farran 



[Oit/ioiia attc'iituilii Fnnan, Proc. Zoul. Soc. Lundon, 1913, p. 

 187, pi. 30, figs. 3-7, 1013.) 



Not found in the Atlantic plankton, but well scattered in 

 the Pacific with numerous large gaps in distribution. It was 

 present in 4 nocturnal and 15 diurnal surface tows, 53 50- 

 meter tows, and 46 100-meter tows. It is thus negative to 

 light, but stops at a depth of 50 meters more often, and with 

 larger abundance records, than at 100 meters. This would be 

 a good species to test for vertical distribution at intervals of 



10 meters, and would probably yield interesting data, espe- 

 cially between the surface and the 50-meter level. 



Oithona brevicornis Giesbrecht 



[Oithona brevicornis Giesbrecht, Atli R. Accad. Lincei, Rome, 

 ser. 4, vol. 7, sem. i, p. 475, i8gi; Fauna und Flora des 

 Golfes von Neapel, vol. 19, pp. 538, 549, pi. 34, figs. 6, 7, 

 1892.] 



Not found in the Atlantic plankton, and virtually confined 

 to the southeastern region of the Pacific. It was taken in 3 

 nocturnal and 3 diurnal surface tows, 6 50-meter tows, and 



11 loo-meter tows. With few exceptions the abundance 

 records were expressed in numerals, indicating that the 

 species is comparatively rare. It is also one of the smallest 

 species, and this, with the short antennae and sharply curved 

 rostrum, will serve to distinguish it. It has been reported by 

 Sewell (1924, p. 792) from the brackish water of Chilka 

 Lake in British India. 



Oithona fallax Farran 



[Oithona jallax Farran, Proc. Zool. Soc. Londiin, 1913, p. 185, 

 pi. 27, figs. 9-12; pi. 28, figs. 1-3, 1913.I 



Not found in the Atlantic plankton and confined to six 

 stations in the Pacific, four in the southeastern region at 

 Merriam Ridge (stations 65 to 68) and two in the central 

 part north of Samoa. It was present in 3 surface tows and 5 

 loo-meter tows, but did not appear in any 50-meter tow. It 

 was originally described by Farran (1913, p. 185) from 

 specimens taken at Christmas Island in the Indian Ocean, 

 but this is the first record from the Pacific. 



Oithona hebes Giesbrecht 



[Oithona hchcs Giesbrecht, Atti R. Accad. Lincei, Rome, ser. 

 4, vol. 7, sem. I, p. 475, 1891; Fauna und Flora des Golfes 

 von Neapel, vol. 19, pp. 538, 549, pi. 34, figs. 8, 9, 1892.] 



This species was not present in the Pacific plankton and 

 was found only at station 30 in the Caribbean Sea, in the 

 loo-meter tow. It has very short first antennae and a swollen 

 metasome, giving it much the appearance of Cyclops. It has 

 been reported from the tropical Pacific by Giesbrecht (1892, 

 p. 538), but this is the first record from the tropical Atlantic. 



Oithona linearis Giesbrecht 



[Oithona linearis Giesbrecht, Atti R. Accad. Lincei, Rome, ser. 

 4, vol. 7, .sem. I, p. 475, 1891; Fauna und Flora des Golfes 

 von Neapel, vol. 19, pp. 538, 548, pi. 34, figs, i, 2. 1892.] 



Two specimens were found in the loo-meter tow at station 

 68 in the southeastern Pacific, and this was the only record 

 for the cruise. It was originally reported from the tropical 

 Pacific, the specimens obtained by Giesbrecht and afterward 

 by Wolfenden (1911, p. 363) having been taken in vertical 

 hauls from depths of 400 to 4000 meters. This fact helps to 

 explain its scarcity in the Carnegie plankton, and it must be 

 regarded as a deep-water form. 



Oithona plumifera Baird 



[Oithona phimijcra Baird, The Zoologist (Newman), vol. i, 

 p. 59, 1843,] 



This species was well distributed in both oceans, but was 

 not present at stations 10 to 18 {.\tlantic), 58 to 68 (except 

 62) and 115 to 137 (Pacific). It was taken in 8 nocturnal 

 and 20 diurnal surface tows, 65 50-meter tows, and 53 100- 

 meter tows. It is probably more or less indifferent to ordinary 

 light, but becomes negative to strong light and shows a 

 preference for the 50-meter tow rather than the loo-meter 

 tow. The characteristic plumes are usually lacking in pre- 

 served material. 



Oithona robusta Giesbrecht 



[Oithona robusta Giesbrecht, Atti R. Accad. Lincei, Rome, ser. 

 4, vol. 7, sem. I, p. 476, 1891; Fauna und Flora des Golfes 

 von Neapel, vol. 19, pp. 538, 549, pi. 34, figs. 4, 5, 16, 17, 

 1892.] 



A few females of this species were obtained in the 100- 

 meter tow at station 157 in the tropical Pacific, and this was 

 the only record for the cruise. It is the largest and stoutest of 

 the species, and has a long and sharply pointed rostrum, 

 curved over ventrally so that it is visible in dorsal view. It 

 was originally obtained from the tropical Pacific a little 

 farther west than this Carnegie location. 



Oithona setiger Dana 



[Oithona setiger Dana, U. S. Exploring Exped., 1838-1842 

 (Wilkes), vol. 14, pt. 2, Crustacea, p. not, 1853; pi. 76, fig. 

 ba-j. 1S55.] 



This species was present at eight yVtlantic stations and ten 

 Pacific stations. It was taken in 2 nocturnal and 3 diurnal 

 surface tows, 4 50-meter tows, and 1 1 loo-meter tows. The 

 comparatively few specimens obtained thus showed a prefer- 

 ence for the loo-meter depth when migrating away from the 

 light. The 2 nocturnal surface tows indicate ihat the species 

 sometimes visits the surface at night. Giesbrecht's (1891, 

 p. 475; 1892, p. 538) records were from the tropical Pacific 

 and included various depths down to 1000 meters. 



Oithona similis Claus 



[Oithona similis Cl.ius, Die Copepoden-Fauna von Nizza, p. 

 74, iS6().] 



This is the most abundant and most widely distributed 

 species, not only of its own genus but also of all the plankton 

 copepods. It was found at 92 per cent of all localities through- 

 out the cruise, and the number of specimens in many of the 



