Vot.2]  Hsterly.—Copepoda of the San Diego Region. 189 
4&4 Grasping antenna on left. Fifth foot, fig. 41¢, d. 
Coloration: Transparent, without pigment. 
Length: Male, 3.39 mm. 
Occurrence: June 10, 1904, 1 male. 
3. Genus Arietellus Giesbrecht. 
Arietellus Giesbrecht, 1892, pp. 66, 415. 
Rhinealanus (part) T. Scott, 1893, p. 31. 
Arietellus Giesbrecht, 1898, p. 124. 
Last two thoracic segments fused, elongated into a strong 
spine on each side (fig. 42a), front with wedge-shaped process, 
rostral filaments slender. Abdomen of female with 4 segments, 
symmetrical; furea, and appendages with long, richly plumose 
bristles. Anterior antennae of female and the right one of male 
at most 20-jomted, joints 1 and 2, 21-25 fused; grasping 
antenna on the left, 19-jointed, terminal portion 2-jointed. 
Inner ramus of postericr antenna straight, longer than outer; 
mandible uniramous, inner ramus lacking; inner ramus and 
third inner marginal lobe of maxilla lacking, outer ramus long 
and characteristic. Anterior and posterior maxillipeds as in 
Augaptilus except in appendages of bristles (fig. 42c). Rami 
of first to fourth feet 3-jointed; fifth foot of female (fig. 426) 
3-jointed, basals 2-, outer ramus 1-jointed, inner ramus rudi- 
mentary. Fifth foot of male without forceps, basals 2-, outer 
ramus 3-jointed, inner ramus 1-jointed. 
1. Arietellus setosus Giesbrecht. 
Arietellus setosus Giesbrecht, 1892, p. 415, pl. 29, figs. 1, 3-7, 
9-13; pl. 39, figs. 34-36; 1897, p. 254; 1898, p. 124. 
With the characters of the genus. 
Coloration: Terminal expansions of plumose fureal bristles 
red, the remaining portion black. Body orange red, bristles on 
posterior antennae and mouth parts, deep red. 
Leneth: 5.5 mm. 
Occurrence: One female was taken at San Diego, Dee. 
22, 1903. 
