DISCUSSION OF SPECIES 



173 



a station, and when it is restricted to a single depth this may 

 be any one oi the three indiscriminately. Accordingly it must 

 be designated as fairly indifferent to light, but may become 

 negative to the stronger light of the tropics. 



Calanus hyperboreus Kr0yer 



[Ciilaiins hypciborciis Kr0yer, Kong. Danske Vidensk. Sclsk., 

 Naturvidcnsk. og. math. Afh., vol. 7, p. 310, pi. 4, 1S38.] 



As the specific name indicates, this is a boreal species and 

 is confined to northern latitudes. It was not present in the 

 Carnegie plankton from the North Atlantic, but has been re- 

 ported from that region by Giesbrecht (1892, p. 91) and Sars 

 (1925, p. 6). It was taken in the Pacific in 4 surface tows, 11 

 50-meter tows, and 10 loo-meter tows, and development 

 stages were abundant in 3 of the surface tows. Besides being 

 larger than those of the preceding species, both the early 

 stages and the adults were much darker and more opaque. 



Calanus minor (Glaus) 



[Cctocluhis minor Claus, Die freilebenden Copepoden, p. 172, 

 1863.] 



Very widely distributed in both oceans, but with numerous 

 gaps within which it was entirely absent from the plankton. 

 It was present in 1 1 nocturnal and 32 diurnal surface tows, 

 73 50-meter tows, and 66 loo-meter tows. Although it thus 

 shows considerable preference for the two deeper tows, it was 

 nevertheless often equally divided among the three depths. 

 In many of the specimens taken in the tropics the setae of the 

 caudal rami were more densely plumose than usual and 

 tinged with red. 



Calanus propinquus Brady 



[Calanus propinquus Brady, Voyage of H.M.S. Challenger, 

 Zoo!., vol. 8, pt. 23, Copepoda, p. 34, pi. 2, figs. 1-7; pi. 14, 

 figs. 10, II, 1883.] 



In the Atlantic this species was almost entirely confined to 

 the Caribbean region, but it was present in every region of 

 the Pacific. Its distribution in the latter ocean, however, was 

 very irregular, with numerous and extensive gaps. It was 

 found in 7 nocturnal and 6 diurnal surface tov.-s, 18 50-meter 

 tows, and 23 100-meter tows. It thus showed a preference for 

 the deeper tows in the daytime but came to the surface at 

 night. The larger size and the pointed posterior corners of 

 the fifth thoracic segment will distinguish the species. 



Calanus tonsus Brady 



[Calanus tonsus Brady, Voyage of H.M.S. Challenger, ZooL, 

 vol. 8, pt. 23, Copepoda, p. 34, pi. 4, figs. 8-9, 1883.] 



This species was not found in the Atlantic plankton, al- 

 though it has been reported from that ocean both north and 

 south of the equator. In the Pacific it was practically con- 

 fined to the eastern part south of the equator, where it was 

 captured in 2 nocturnal and 2 diurnal surface tows, 3 50- 

 meter tows, and 4 100-meter tows. It was originally reported 

 by Brady (1883, p. 34) as from this locality as well as else- 

 where, and was found by Farran (1929, p. 216) in the Terra 

 Nova plankton south of New Zealand. 



Genus CALOCALANUS Giesbrecht, 1888 



Calocalanus pavo (Dana) 



[Calanus pavo Dana, Proc. Amer. Acad. Arts and Sci., vol. 2, 

 p. 13, 1849; U. S. Exploring Exped., 1838-1842 (Wilkes), 

 vol. 14, pt. 2, Crustacea, p. lofii, 1853; pi. 72, fig. I2«, /;. 

 1855.] 



This species was dispersed everywhere in both oceans 

 except in the extreme northern parts, but usually in small 

 numbers. The distribution, however, was very irregular, with 

 numerous gaps and great variation in abundance. It was 

 present in 5 nocturnal and 53 diurnal surface tows, 78 50- 

 meter tows, and 65 100-meter tows. It is thus more or less 

 indifferent to light and is often equally distributed at all 

 three depths, or any two of them, at the same time. The four 

 enlarged and fanlike plumes on each caudal ramus combined 

 with the profuse armature of the anterior antennae give 

 exceptional beauty to the living copepod. These are always 

 broken off in preserved material, and the specimens have a 

 ragged and uncouth appearance. 



Calocalanus plumulosus (Claus) 

 (Figure 18) 



[Calanus plumulosus Claus, Die freilebenden Copepoden, p. 

 174, pi. 26, figs. 15, 16, 1863.] 



Not present in the Atlantic plankton but fairly well dis- 

 tributed in the Pacific, where it was taken in 10 nocturnal 

 and 5 diurnal surface tows, 25 50-meter tows, and 25 100- 

 meter tows. When alive this copepod carries an enormous 

 plume on the left caudal ramus, but this is never seen on a 

 preserved specimen. Furthermore, all the appendages are so 

 brittle that they are usually broken and it is very rare to find 

 a specimen with anything except the fifth legs intact. For- 

 tunately these legs are quite characteristic and will serve to 

 identify the species. 



Calocalanus styliremis Giesbrecht 

 (Figures 12, 14) 



[Calocalanus styliremis Giesbrecht, Atti R. Accad. Lincei, Rome, 

 ser. 4, vol. 4, sem. 2, p. ^■^^j 1888; Fauna und Flora des 

 Golfes von Neapel, vol. 19, pp. 176, 185, pi. 9, figs. 15, 18, 

 29; pi. 36, figs. 46-48, 1892.] 



Found in the Sargasso and Caribbean regions and widely 

 dispersed in the Pacific. The distribution in the latter ocean 

 is such that the species is of rare occurrence although found 

 44 times from station 40 to station 159. It was taken in 16 

 diurnal surface tows, 32 50-meter tows, and 23 loo-meter 

 tows. It is thus negative at least to strong light. 



Genus CANDACIA Dana, 1846 



This is a temperate and tropical genus and was not found 

 north of latitude 50° in the Atlantic or 40° in the Pacific. 

 Several of the species have a world-wide distribution and 

 most of them were more abundant in the deeper tows than 

 at the surface. See chart 4, on following page. 



