Vou.2] Esterly—Copepoda of the San Diego Region. 203 
proximal portion; joints nineteen and twenty-one and twenty- 
two and twenty-five fused. Right fifth foot 3- to 4-jointed, 
forceps not complete, the left 3-jointed, seldom with rudiment of 
Inner ramus. 
1. Genus Acartia Dana. 
Acartia Dana, 1846, p. 183; 1852, p. 118. 
Dias Brady, 1883, p. 72. 
Dias Lilljeborg, 1853. 
Dias Claus, 1863, p. 191. 
Dias Brady, 1883, p. 72. 
Acartia Thompson, 1888a, p. 149; 1888b, p. 141. 
Acartia Giesbrecht, 1892, pp. 75, 506, 721; 1898, p. 150. 
Acartia Dahl, 1894ce, p. 13. 
Acartia Wheeler, 1899, p. 182. 
Fifth thoracic segment and abdomen of male symmetrical ; 
latter with shortened anal segment. Antennae of female with 
seventeen segments, of the same diameter throughout the length; 
grasping antenna of male with very slightly thickened middle 
joints. Outer ramus of posterior antenna much shorter than 
the inner; second joint of inner elongated, first joint with nine 
bristles on the inner border. Outer ramus of mandible articu- 
lates in the middle of the margin of the second basal. First 
outer marginal lobe of maxilla with long bristles, outer ramus 
rudimentary, its place supplied by two bristles. Proximal lobes 
of anterior maxillipeds well developed, with long bristles; pos- 
terior maxilliped with four joints. Inner ramus of first pair of 
feet with two joints, fifth pair of female without inner ramus, 
with long outer terminal bristle on second basal. 
° Cephalothorax with five segments, last two fused.- Pos- 
terior antenna very slender, second basal joint fused with prox- 
imal joint of inner ramus, mandible with weak blade, which 
has seven teeth. Posterior maxilliped without outer marginal 
bristies, and with three inner marginals on third joimt. Outer 
ramus of first to fourth pairs of feet 3-jointed, first basal 
without bristles, second with rather long outer marginal bristle 
in fourth pair. The very much stunted fifth pair (fig. 49d) 
consists on each side of two or three joints; the end joint (outer 
ramus) is a thick stylet-shaped bristle, and on the outer border 
of the second basal is a slender feathered bristle. 
