1913] Esicrhj: Copepoda of the San Diego Region 1S9 



half times as long as the abdomen and furea. The .genital seg- 

 ment is markedl.y protuberant on the ventral border ; this segment 

 is as long as the rest of the abdomen and the furea (pi. 10, 

 fig. 10). 



The anterior antennae are 24-jointed and slightly longer than 

 the cephalothorax. The inner ramus of the posterior antennae 

 is between two and three times as long as the outer. The mandi- 

 bular blade is shown in plate 11, figure 34, and the anterior and 

 posterior maxillipeds in figures 41 and 36 respectively. The 

 bristles of the maxillipeds do not have the cups or "biittons" 

 so generally found in this genus. The feet do not appear to be 

 unusual. Figures 50 and 60 of plate 3 show the outer ramus of 

 the first foot and the fifth foot respectively. 



Length: 6.1 mm. (cephalothorax 5 mm.). 



Coloration : Transparent, but the plumose bristles of the 

 posterior antennae and the mandible and those of the furea are 

 iridescent. 



Occurrence : Hauls 1524 and 2569. 



This species appears to resemble A. nodifrons (Sars, 1905, 

 p. 13), which is also arostrate and without the buttons on the 

 bristles of the maxillipeds. 



Arietellus pacificus n. sp. 



PI. 10, figs. 9, 23; pi. 12, figs. 46, 55 



Adult female. The head is smoothly rounded, with an incon- 

 spicuous crest. The rostral filaments are delicate but straight 

 and rather stiff (pi. 10, fig. 0). The sides of the last thoracic 

 segment are rounded, as shown in plate 10, figure 23 ; this figure 

 also shows the proportionate lengths of the abdominal segments 

 and furea. 



The anterior antennae are 19-.jointed, and as carried on the 

 body reach to the posterior border of the second thoracic segment. 

 The fir.st joint of the antenna is as long as the next eight together. 

 The outer ramus of the first foot (pi. 12, fig. 46) shows distinctive 

 characters. The fifth foot (pi. 12, fig. 55) is also of use in the 

 recognition of the species. 



