DISCUSSION OF SPECIES 



191 



brecht (i8g8, p. 135). It vvas taken in 4 nocturnal and 2 

 diurnal surface tows in the southeastern Pacific, and appar- 

 ently stays at the surface throughout the entire 24 hours. 

 Head with median crista which is curved anteriorly into a 

 hook; abdomen and caudal rami symmetrical. It was found 

 in more than fifty of the Sihoga plankton collections, in one 

 of which the number of specimens obtained was 200 and in 

 another 440, showing that this species, like deUunccita, is 

 more or less gregarious. 



Labidocera acutifrons (Dana) 



(Figure 52) 



[PoiitclLi iicntijroiis Dann, Proc. Amer. Acad. Arts and Sci., 



vol. 2, p. 30, 1849.] 

 [PontcUina acutifrons Dana, U. S. Exploring E.xped., 1838-1842 



(Wilkes), vol. 14, pt. 2, Crustacea, pp. 1149, 1150, 1853; pi. 



80, fig. iia-h, 1 855. 1 



Not present in the Atlantic plankton, but found in the 

 southeastern and central Pacific. Taken in 7 diurnal surface 

 tows, I 50-meter tow, and i loo-meter tow, also recorded as 

 common in one of the nocturnal surface tows. Head with a 

 median crista which is not hooked; abdomen and caudal 

 rami quite asymmetrical. This species has been reported 

 from the tropical and temperate Atlantic, both north and 

 south of the equator, by Ciiesbrecht (1892, p. 445) and Sars 

 (1925. P- 354)- 



Labidocera detruncata (Dana) 

 (Figures 53, 6g) 



[Pontclhi ih-tntncata Dana, Proc. Amer. Acad. Arts and Sci., 



vol. 2, p. 29, 1S49.] 

 [PontcUina detruncata Dana, U. S. Exploring Exped., 1S38- 



1842 (Wilkes), vol. 14, pt. 2, Crustacea, pp. 1143-1145. 1853: 



pi. So, fig. 7(7-;, 1855.1 



Not found in the Atlantic plankton, but the most abun- 

 dant species of the genus in the Pacific, and found every- 

 where except in the northern and southern parts, stations 52 

 to 70 and 116 to 128. It was taken in 6 nocturnal and 68 

 diurnal surface tows, 11 50-meter tows, and 7 loo-meter 

 tows. It is a surface species, and both adults and development 

 stages often swarm at the surface and constitute the bulk of 

 the surface copepods. The females are easily identified by 

 the peculiar asymmetry of the urosome and the males by 

 the structure of the fifth legs. It was reported by Brady 

 (1883, p. 90) from both the North and South Atlantic. 



Labidocera nerii (Kr0yer) 



(Figure 86) 



[Pontia ncrii Kr^yer, Naturhist. Tidsskr., KjcJbenhavn, ser. 2, 

 vol. 2, p. 600, 1849.1 



Found at four stations in the Atlantic and three in the 

 Pacific, all widely separated. It was present in 4 surface tows, 

 2 50-meter tows, and 2 100-meter tows. It can be distin- 

 guished from the other species by the structure of the fifth 

 legs. As far as is known, this is the first record of the species 

 from the Pacific Ocean, the four stations being in the tropics. 



Labidocera woUastoni (Lubbock) 



(Figure 95) 



[Puntclla woUastoni Lubbock, Ann. and Mag. Nat. Hist., ser. 

 2, vol. 20, p. 406, pis. 10, II, 1857.] 



Not present in the Pacific plankton, but taken at two of 

 the Atlantic localities in the surface tow. The specimens 

 were not iuUy developed, but the fifth legs showed the dis- 

 tinctive structure of this species. Apparently it has never 

 been reported from the Pacific Ocean. 



Genus LOPHOTHRIX Giesbrecht, 1895 



Lophothrix frontalis Giesbrecht 



[Lophothrix frontalis Giesbrecht, Bull. Mus. Comp. Zool., 

 Harvard Coll., vol. 25, no. 12, p. 254, pi. 2, figs. 1-5, 9-12, 

 1895.] 



A single specimen was captured in the vertical tow from 

 1000 meters at station 64. This is a deep-water species and 

 probably has a much wider distribution than the solitary 

 capture would suggest, since this was the only time the tow 

 nets went below 100 meters. The prominent median crest on 

 the forehead and the structure of the fifth legs identify the 

 species. It was reported as common in deep hauls oft the 

 California coast by Esterly (1906, p. 65). 



Lophothrix humilifrons G. O. Sars 



[Lophothrix Jitimdijrons G. O. Sars, Bull. Mus. oceanogr. 

 Monaco, no. 26, p. 22, 1905.] 



A single specimen was captured in the same vertical tow 

 as the preceding species. This is another deep-water form 

 and, like frontalis, is probably more widely distributed at 

 depths below too meters. It can be distinguished by its ob- 

 tusely rounded forehead, which shows no trace of a median 

 crest. This species has been reported only by Sars (1925, 

 p. 166), who found it common in deep hauls in the tem- 

 perate Atlantic. 



Genus LUBBOCKIA Claus, 1863 



Lubbockia aculeata Giesbrecht 



[Lubbockja aculeata Giesbrecht, Atti R. Accad. Lincei, Rome, 

 ser. 4, vol. 7, sem. i, p. 477, 1891; Fauna und Flora des 

 Golfes von Neapel, vol. 19, pp. 606, 611, pi. 48, figs. 3, g, 13, 

 17, 20, 1892.] 



Found at a single station (15) in the Adantic and at 

 twentv-one widely separated localities in the Pacific. It was 

 taken in i nocturnal surface tow, 13 diurnal 50-meter tows, 

 and 15 100-meter tows. It was not present at the surface in 

 the daytime and is therefore negative to light, but migrates 

 to the surface sometimes at night. This species is longer and 

 more slender than squillimana, and the posterior margins of 

 the urosome segments are fringed with small spines. All but 

 2 of the specimens taken in the Siboga plankton were cap- 

 tured in vertical hauls from depths of 900 to 1500 meters, 

 and Wolfenden's (1911, p. 363) single record was from a 

 vertical haul from a depth of 3000 meters. 



