DISCUSSION OF SPECIES 



189 



meter tows, 70 loo-meter tows, and the vertical low from 

 1000 meters at station 64, but not in any of the surface tows. 

 The distal half of each first antenna is very slender and looks 

 fragile, but it must be exceptionally tough, since it usually 

 remains intact in the preserved specimens although the two 

 antennae are often intricately entangled with each other and 

 with the other appendages. The absence of the species from 

 all nocturnal surface tows indicates that it does not take part 

 very often in the upward migration at night. The northern 

 boundary of the species as given by Giesbrecht (1892, p. 384) 

 and Sars (1925, p. 240) (latitude 26° north) is extended by 

 these Carnegie records to latitude 34° north in the Pacific 

 and to 42° north in the Atlantic. 



Haloptilus ornatus (Giesbrecht) 



[Hemicalanus ornuttis Giesbrecht, Fauna und Flora des Golfes 

 von Neapel, vol. 19, pp. 384, 399, pi. 27, figs. 16, 17, 25; pi. 

 42, figs. 2, 27, 28, 1892.] 



This species was found at nine Atlantic and nine Pacific 

 stations, the Atlantic localities being in the Sargasso and 

 Caribbean regions, the Pacific localities widely scattered. It 

 was present in 4 50-meter tows and 14 loo-meter tows, and 

 was recorded as common five times. It was originally taken 

 in the Mediterranean, but has been reported by several 

 authors from the Atlantic and Pacific oceans. Only 2 speci- 

 mens were obtained in the Siboga plankton, both in vertical 

 hauls from depths of 700 to 900 meters. 



Haloptilus oxycephalus (Giesbrecht) 



[Hemicahuuis oxycephalus Giesbrecht, Atti R. Accad. Lincei, 

 Rome, ser. 4. vol. 5, sem. i, p. 813, iS8g; Fauna und Flora 

 des Golfes von Neapel, vol. 19, pp. 384, 398, pi. 42. figs. 7, 

 16, 23, 1892.] 



A single specimen of this species was found in the 100- 

 meter tow at each of two stations, 70 and 74, in the eastern 

 tropical Pacific, and it has also been reported from the trop- 

 ical Pacific by Giesbrecht (1892, p. 384). Yet Farran (1929, 

 p. 268) has recorded it from both sides of the Antarctic 

 Circle in the South Pacific, so that it cannot be considered as 

 exclusively tropical. Nearly all the specimens previously ob- 

 tained were taken in vertical hauls from deep water, and the 

 species was nowhere abundant. 



Haloptilus plumosus (Claus) 



[Hemicalanus plumosus Claus, Die frcijebenden Copepoden, 

 p. 178, pi. 28, fig. 12; pi. 29, figs. 4-7, 1863.] 



This species was found at one Atlantic station and at 

 eighteen widely separated Pacific stations, and in them was 

 strictly confined to the 100-meter tow, though present in the 

 vertical tow from 1000 meters at station 64. Its failure to 

 appear above the 100-meter level suggests that it is bathy- 

 pelagic, and this conclusion is supported by the fact that all 

 the specimens previously reported have been captured at a 

 depth varying from 400 to 3000 meters, .-^s far as all the 

 records show, these 100-meter tows are the nearest to the 

 surface it has ever been taken. 



Haloptilus spiniceps (Giesbrecht) 



[Heniiaihinus spiniceps Giesbrecht, Fauna und Flora des 

 Golfes von Neapel, vol. ly, pp. 384, 399, pi. 27, figs. 5, 20, 

 35,40; pi. 42, figs. 3, 8, 10, 11,21,25, 1892.] 



This species, like plumosus, was found at a single Atlantic 

 station and at widely separated localities in the Pacific. It 

 was taken in 13 50-meter tows and 16 100-meter tows, but 

 80 per cent of the abundance records were numerals. Hence, 

 although fairly widespread, the species is nowhere abundant, 

 and its complete absence from the surface at night as well as 

 in the daytime indicates infrequent nocturnal migrations. 

 The characteristic spiny projection from the forehead is often 

 found telescoped into the head in preserved material, making 

 the identification of the species difficult. 



Genus HETERAMALLA G. O. Sars, 1907 



Heteramalla dubia (T. Scott) 



[Amallophora dubia T. Scott, Trans. Linn. Soc. London, ser. 2, 

 Zool., vol. 6, pt. I, p. 55, pi. 4, figs. 1-18, 1894.] 



A few specimens were obtained in the loo-meter tows at 

 stations 56 and 153 in the southeastern and central Pacific, 

 and these were the only localities during the cruise. The 

 species was originally reported by T. Scott ( 1894, p. 55) from 

 the Gulf of Guinea and included males only. A female was 

 afterward found in the Siboga plankton and described by 

 A. Scott (1909, p. 86), and both sexes were captured in the 

 North Atlantic during the Monaco expeditions and described 

 by Sars (1925, p. 142). All these specimens were taken in 

 vertical hauls from depths of 1500 to 5000 meters. 



Genus HETERORHABDUS Giesbrecht, 1898 



This is a deep-water genus, and with a single exception 

 none of its species was found at the surface, whereas two of 

 them were confined to the single looo-meter haul at station 

 64. The genus was fairly well distributed in both oceans, 

 however, especially in the Pacific, a fact which is the more 

 noteworthy in that most of the specimens hitherto reported 

 came from depths considerably below 100 meters. It belongs 

 chiefly to the temperate and tropical zones, although speci- 

 mens have been obtained from both polar oceans. The single 

 specimen of the species papiUiger taken in a nocturnal sur- 

 face tow indicates very meager participation in the upward 

 migrations at night. The genus may be easily recognized by 

 the asymmetry of the caudal rami and the excessive length 

 of one seta on the left ramus. 



Heterorhabdus abyssalis (Giesbrecht) 



[Hcterochacta abyssalis Giesbrecht, Atti R. Accad. Lincei, 

 Rome, ser. 4, vol. 5, sem. i, p. cSi2, 1889; Fauna und Flora 

 des Golfes von Neapel, vol. 19, pp. 373, 382, pi. 19, fig. 4; 

 pi. 20, figs. 29, 30, 1892.] 



Three specimens were taken in the vertical tow from 1000 

 meters at station 64. This species has been obtained only 

 from considerable depths, as its name implies, and hence it 

 would not be likely to occur in the Carnegie plankton except 



