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PACIFIC SCIENCE, Vol. IX, October, 1955 
posterior margins of segments 23 and 24 of 
the first antennae are distinctly segmented 
even in the early copepodite stages; in C. 
tenuicornis there is no trace of segmentation. 
Finally, in the two larger species, the proximal 
part of the outer margin of the third exopodal 
segment of the second to fourth swimming 
legs of the male is serrate; in C. tenuicornis 
these margins are smooth. 
Sars (1925: 7) erected a new genus, Neo- 
calanus , which he did not define, to include 
tenuicornis , gracilis , and robustior. Although 
modern authors differ as to the validity of 
Neocalanus , almost all are agreed that tenui- 
cornis should not be placed in it. Neocalanus 
was first defined by Verwoort (1946: 39); his 
definition, which includes the hooked spine 
of the first swimming legs and the serrations 
on the second to fourth swimming legs, def- 
initely excludes tenuicornis . 
C. tenuicornis is widely distributed in tropical 
and temperate waters, although it is not ordi- 
narily taken in very large numbers. Verwoort 
(1946) has summarized distribution records 
from the literature. It is sparingly distributed 
throughout the Atlantic from about 52° N. to 
20° S., with northern record from the Faroe 
Banks. It is found in all parts of the Medi- 
terranean. In the Indo-Pacific it ranges from 
about 42° N. to 52° S. Wilson’s (1942) records, 
not mentioned by Verwoort, show it to be 
widespread in the Eastern Pacific, within about 
the same latitudinal boundaries. It is not 
usually a common species in the East Indies. 
Cleve (1904) records it from both east and 
west of South Africa. Ordinarily it is an 
epiplanktonic form. 
Calanus lighti new species 
Figs. 1, 2 
This species is named in honor of the late 
S. F. Light of the University of California, 
Berkeley. 
adult female: Length, excluding furcal 
setae, 2.32-3.08 mm. Body form similar to 
C. tenuicornis , but longer and more slender in 
appearance. Ratio of length to depth of ce- 
phalothorax about 6:1 as opposed to 4.5:1 
in C. tenuicornis. Head with more flattened 
dorsal slope (lateral view) than in tenuicornis . 
Head separated from first thoracic somite by 
weakly developed suture. Posterior border of 
head raised into a small, slightly backward- 
curved process in dorsal midline. Thorax 
about one fourth longer than head; second 
and fourth somites each with two pairs of 
setae on either side of median dorsal line, 
anterior pair longer; third somite with two 
pairs of equal-sized dorso-lateral setae; fifth 
somite rounded posteriorly, slightly over- 
lapping genital somite. Genital somite pro- 
duced into somewhat flattened hump ven- 
trally, less produced than in tenuicornis. Ab- 
dominal somites much longer in proportion 
to their depth than in tenuicornis\ somite 2 
about one third longer than somite 3 (only 
one fourth longer in tenuicornis ) . Furcae about 
2.5 times as long as wide; the four apical 
setae very long, especially the next to inner- 
most one, which is about twice as long as 
the others; lateral setae very short. 
First antennae more than twice as long as 
body; segments 3, 7, 14, 18, 21, and 24 bear 
elongate setae anteriorly; segments 23 and 24 
each bear a very long feathered seta on the 
posterior surface. 
Setae of mouth parts, especially those of the 
terminal segments, very long. Setae of exopod 
of first maxilla very long, feathered, and 
pigmented. 
First swimming leg with triangular pro- 
jection on proximal part of posterior surface 
of first segment of exopod. Posterior part of 
distal margin of first segment of endopod 
produced into a number of minute linear 
processes in the specimen drawn, not in other 
specimens examined. Medial margin of first 
basipod of fifth swimming leg smooth, with- 
out setae. 
ADULT male: Length, excluding furcal 
setae, 1.90-2.68 mm. Body a little shorter 
and less slender than in female. Head more 
rounded in lateral view. Third thoracic somite 
with two pairs, fourth somite with one pair 
