128 University of California Publications. [ ZooLoey 
Length: Female, 1.8-2 mm.; male, 1.5-1.8 mm. 
Occurrence: Fairly abundant, both in summer and winter 
collections. 
4. Calanus gracilis Dana. 
Calanus gracilis Dana, 1849, p. 278; 1852, p. 1078; 1855, pl. 
74, fig. 10. 
Cetochilus longiremis Claus, 1863, p. 171, pl. 26, fig. 1. 
Calanus gracilis Brady, 1883, p. 35, pl. 5, figs. 1-6; pl. 6, fig. 10. 
Calanus gracilis Giesbrecht, 1892, pp. 90, 128; pl. 6, fig. 1; pl. 7, 
fig. 26; pl. 8, figs. 2, 4, 6-8, 12, 16, 26; 1898, p. 17. 
ene tore 
Fig. 4.—Calanus gracilis. (a) Genital segment of female, lateral, x83. 
(6) Outer margin of first basal of anterior maxilliped of 
female 140. 
2 Head fused with thorax; forehead and sides of last thoracic 
segment rounded. Left side of furca with one elongated bristle. 
Anterior antennae at least 114 times as long as the body. There 
is a process at the base of the inner marginal bristle of the second 
basal of the second foot (ef. fig. 5d). The proximal outer marginal 
spine of terminal joint of outer ramus in second to fourth feet, 
respectively, divides the margin into portions as 1:1, 4:3, 4:3 in 
length. First basal of fifth pair with feathered inner margin. 
4&4 Head separate from thorax, anterior antennae straight, 
joints 1 and 2, 24 and 25 fused. Mouth parts greatly reduced. 
Outer border of third joint of outer ramus denticulate in second 
to fourth feet. Right foot of fifth pair and inner ramus of the 
left as in the preceding pairs; basals and first two joints of left 
foot elongate, third joint shortened, no bristle on inner border of 
outer ramus. 
Coloration: Transparent, with little or no pigment in body. 
Length: Female, 2.4 mm. 
Occurrence: San Diego, July 14, 1903, one female; December 
23, 1903, 14 females. 
