416 
PACIFIC SCIENCE, Vol. IX, October, 1955 
of dorso-lateral setae, larger than those of the 
female. Furcae usually widely divergent. 
First antennae about 1.5 times as long as 
body; segments 1-2, 3-5, 7-8, and 24-25 
fused. 
Mouth parts reduced, some of setae re- 
duced in size or absent. Second antennae 
without setae on proximal segment of endo- 
pod. Gnathal lobe of mandible much smaller 
and more weakly chitinized than in female; 
teeth only slightly developed; terminal seg- 
ment of endopod with only nine setae. First 
maxilla thinly chitinized in comparison with 
that of female; spines on gnathal lobe re- 
duced. 
Fifth swimming legs as in C. tenuicornis; no 
setae on inner margins of exopods; distal 
segment of left exopod pyriform, with slender 
terminal spine. 
types: The types, all from CCOFI cruises, 
have been deposited in the United States Na- 
tional Museum. They are listed in Table 1. 
Over 100 specimens of C. tenuicornis from 
CCOFI cruises have been added to the United 
States National Museum collections. 
Eight paratypes of C. lighti and 11 speci- 
mens of C. tenuicornis have been deposited at 
the Scripps Institution of Oceanography, La 
Jolla, California. Seven paratypes of C . lighti 
and 18 specimens of C. tenuicornis have been 
sent to the Allan Hancock Foundation, Uni- 
versity of Southern California. 
remarks: C. lighti is most readily disting- 
uished from C. tenuicornis by the shape of the 
body in lateral view. In addition to the gen- 
erally more slender and elongate form, the 
new species is characterized by the more pro- 
nounced dorsal elevation at the posterior 
margin of the head and the ratio of length to 
depth of the abdominal somites. The males 
of the two species are less easily distinguished 
than the females. Where the two species occur 
together the differences in size and form are 
readily discernible in both sexes. If only one 
species is present, it can be assumed that the 
males are conspecific with the usually much 
more numerous females. 
The posterior process on the first segment 
of the exopod of the first swimming leg (Fig. 
2f) apparently has not been recorded pre- 
viously from calanoid copepods, probably 
because of its inconspicuousness. It is, how- 
ever, not limited to the species treated in this 
paper, for I have observed a similar, less 
pronounced process in Calanus gracilis , C. 
rohustior , C. finmarchicus , and Undinula vulgaris 
but not in Calanus minor . Possibly it is of 
rather widespread occurrence. A somewhat 
similar process on the posterior aspect of the 
second basal segment of the first swimming 
leg is reported by Sewell (1947: 165, text fig. 
49) for members of the family Metridiidae. 
Without exception, the furcae in all the 
specimens of C. tenuicornis and C . lighti that 
I have examined contained a number of 
TABLE 1 
DATA ON TYPES OF Calanus lighti SP. NOV. 
CRUISE 
STATION 
USNM NO. 
Holotype 
9, 
1 
5 
1008 
28° 50' N 
121° 
19' W 
97109 
Allotype 
d\ 
1 
5 
1008 
28 50 
121 
19 
97110 
Paratypes, 
16 
5 
1008 
28 50 
121 
19 
97111 
66 
6 
807 
32 05 
124 
55 
97112 
20 
9 
1204 
26 16 
117 
03 
97113 
88 
9 
1009 
28 31 
121 
52 
97114 
3 
4 
1105 
28 04 
118 
36 
97115 
5 
20 
120.110 
25 33 
119 
44 
97116 
50 
9 
1011 
27 56 
122 
59 
97117 
