Vou.2]  Esterly.—Copepoda of the San Diego Region. 143 
Clausocalanus arcuicornis Giesbrecht, 1888, p. 334; 1892, pp. 186, 
1985 pl ios 1a pig; fig 7; pl.) 10; figs: 3-8, 14, 16, 17, 
19; pl. 36, figs. 29-31, 34; 1898, p. 27. 
Clausocalanus arcuicornis Wheeler, 1899, p. 171, fig. 9. 
b 
Ee 
: 2) 
Fig. 13.—Clausocalanus areuicornis. (a) Male, lateral, X45. (b) Second 
basal of second foot to show toothed distal margin, 410. 
(c) Fifth foot of male X83. 
2 Genital segment longer than the two following. Furea 
about as long as broad. No aesthetask on fourth, sixth, eighth, 
eighteenth or twenty-second joints of the anterior antennae. 
& Second segment of abdomen at least as long as the third 
and fourth together (fig. 13a) ; right foot of fifth pair with three 
joints (fig. 138c). 
Coloration: Not very transparent, with red pigment in vari- 
ous places on the posterior part of the body and on genital seg- 
ment. 
Occurrence: San Diego, June 25, 1904, one male. 
Sub-fam. AETIDIINAE. 
Aetidiina Giesbrecht, 1892, p. 52. 
Aetidiinae Wolfenden, 1903, p. 263. 
2 Head sometimes distinct from first thoracic segment ; other- 
wise the cephalothorax always has four segments, as has the 
