. Bulletin - United States National Museum. Science. COPEPODS OF THE WOODS HOLE REGION 169 Male.—Shorter and narrower than the female; fourth and fifth segments distinctly separated; urosome 5-segmented and nearly sym- metrical, the right caudal ra- mus a trifle larger than the left, with a tuft of stiff bris- tles on the outer margin; end segment of left fifth leg twice as long as penultimate segment; thumb of chela on right leg club-shaped, with subterminal spine. Total length, mm. Remarks. — This species may be recognized by the prevailing symmetry of the body and by the details o
. Bulletin - United States National Museum. Science. COPEPODS OF THE WOODS HOLE REGION 169 Male.—Shorter and narrower than the female; fourth and fifth segments distinctly separated; urosome 5-segmented and nearly sym- metrical, the right caudal ra- mus a trifle larger than the left, with a tuft of stiff bris- tles on the outer margin; end segment of left fifth leg twice as long as penultimate segment; thumb of chela on right leg club-shaped, with subterminal spine. Total length, mm. Remarks. — This species may be recognized by the prevailing symmetry of the body and by the details of the fifth legs. Williams found it abundant in Nar- ragansett Bay and Charles- town Pond, and further search will probably reveal its presence in other ponds around Woods Hole beside . Figure 115.—Tortanus setaoaudatus: a. Female, the two mentioned above. dorsal; i, female, fifth legs; c, male, fifth legs. Suborder HARPACTICOIDA Fifth thoracic segment firmly attached to the sixth segment, but forming a movable articulation with the fourth segment. Posterior body usually about as wide as the anterior, and both divisions more or less cylindrical. Genital openings paired in both sexes, and on the ventral surface of the genital segment; one or two ovisacs. First antennae short, rarely more than 8- or 9-segmented, both prehensile in the male; second antennae biramose, the exopod 1- to 7-segmented. rarely obsolete; mandibles and first maxillae with a palp; second maxillae with digitiform processes; maxillipeds usually prehensile. First legs in the majority of cases more or less transformed into grasping organs, next three pairs natatory; fifth legs never natatory, but lamellar and usually 2-segmented, the basal segment enlarged on its inner margin into a broad expansion, both segments armed with plumose setae or spines, or both. In this group, as in the Calanoida, the number of segments in the rami of the swimming legs is not always constant in all species of a given genus; th
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