. Bulletin - United States National Museum. Science. 30 BULLETIN' 15 8, UNITED STATES NATIONAL MUSEUM rical; first antennae just reaching the caudal rami; inner margin of fifth basipods armed with setae. Outer margin of second segment of second exojDod with a deep notch at its proximal corner, armed with a spine. Total length, ^ mm. Male.—Head fused with first segment; first antennae curved in the form of an S, and a little longer than in the female. Eight fifth leg very short, endopod 3-segmented, without setae and tipped Avith two spines; exopod 3-segmented, without setae, but with a
. Bulletin - United States National Museum. Science. 30 BULLETIN' 15 8, UNITED STATES NATIONAL MUSEUM rical; first antennae just reaching the caudal rami; inner margin of fifth basipods armed with setae. Outer margin of second segment of second exojDod with a deep notch at its proximal corner, armed with a spine. Total length, ^ mm. Male.—Head fused with first segment; first antennae curved in the form of an S, and a little longer than in the female. Eight fifth leg very short, endopod 3-segmented, without setae and tipped Avith two spines; exopod 3-segmented, without setae, but with a process on the outer margin of the middle segment, shaped like a slender finger. Left fifth leg without an endopod, the second basipod segment greatly elongated, the exopod enlarged and 3-seg- mented, the basal and second segments armed with long, sharp-. FiGUEB 14.—Undinula vulgaris: a. Second segment of second exopod; 6^ fifth legs of male; c, fifth leg of female pointed, curved claws, the terminal segment tipped with a wormlike process. Total length, mm. Remarks.—This species, like the preceding one, prefers the trop- ical parts of the ocean, but goes north in the Atlantic at least to latitude 41° N. Although it is very cosmopolitan and is found in all the oceans, the present is the first record of its occurrence on our American shores. The highly modified fifth legs of the male, the elongated left fifth exopod of the female, and the peculiar invagina- tion of the second exopod in both sexes furnish convenient characters for the identification of the species. Genus EUCALANUS Dana, 1852 Head triangular, often elongated and fused with the first segment; rostrum produced into threadlike filaments; first antennae reaching beyond the caudal rami, sometimes unequal in length, with colored plumose setae at their tips; endopod of second antennae longer than exopod. Exopods of first four pairs of legs 3-segmented, first endopod 2-segmented, the next three 3-segmented;
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