Vou.2]  Esterly—Copepoda of the San Diego Region. 209 
on the first and second joints, two on the third; proximal bristle 
of outer margin of third joint of third and fourth pairs reduced. 
4 Genital segment broad (figy505). Proximal joint of distal 
portion of anterior antennae with a half crescentic process on 
the inner margin. Third joint of outer ramus of first and 
fourth pairs of feet with two outer marginal bristles, the second 
and third with three (fig. 50c). 
Coloration: Giesbrecht shows red pigment in body, and 
especially in long bristles of anterior antennae, furea, feet and 
mouth parts, while other animals may be colorless. All speci- 
mens I have seen are colorless. 
Leneth: Female, 1-1.4 mm.; male, 0.75-1 mm. 
Occurrence: Not as abundant as O. nana, but some speci- 
mens occur in all catches where the ordinary Podoplea are num- 
erous, Summer and winter. 
2. Oithona nana Giesbrecht. 
Oithona nana Giesbrecht, 1892, p. 549, pl. 4, fig. 8; pl. 34, figs. 
10, 11, 20, 24, 26, 34, 35, 42; pl. 44, figs. 2, 4. 
Fig. 51.—Oithona nana. (a) Male, dorsal, X83. (b) Third joint of outer 
ramus of first foot of female X83. (c) Third joint of outer 
ramus of fourth foot of male 83. 
