398 PROCEEDINGS OF THE NATIONAL MUSEUM. voi.xxxm. 



ing to the lateral processes in the male. The second pair of dorsal 

 plates are much shorter and fit inside the wings of the first pair; 

 there is only a shallow emargination (no sinus at all) on their poste- 

 rior border to indicate their dual origin.. The third pair are more 

 deeply incised, a trifle wider, and considerably longer; the sinus 

 between them is broad and evenly rounded. 



Genital segment subquadrate, narrowed a little posteriorly and 

 armed with a minute spine on either side just in front of the poste- 

 rior corners, which are obliquely truncated. The posterior margin 

 of this segment, instead of having a single deeply rounded sinus at 

 the center, as in most species, has two shallow sinuses, one on either 

 side, meeting at the center in a point which projects backward over 

 the abdomen. The anal laminae project from beneath the center of 

 these sinuses and are about three times the length of the dorsal plate 

 of the sixth segment. 



They are only slightly divergent, with the outer margins straight, 

 while the inner ones are armed Avith the usual wings, dentate near 

 their posterior ends. Sixth segment plate \vider than long, with an 

 evenly rounded margin; abdomen very small, its ventral plate 

 scarcely projecting beliind its posterior border. 



The two joints of the first antennae about equal; no setae on the 

 basal joint and only a few on the terminal; second antennae stout, 

 the terminal claw with a swollen base and a sharp curve close to the 

 tip; no accessory spines. The adhesion pads relatively small, the 

 first two pairs about the same size and shape, circular, the fourth 

 pair narrow elliptical, twice as long as wide. Second maxillae trian- 

 gular, short and very blunt; first maxillipeds stout and fleshy, the 

 two joints of nearly the same length, as are also the two claws at the 

 tip of the terminal joint. Second pair large and much swollen, with 

 the distal knob of the pincher jaws several times the size of the 

 proximal one. Basal joint of the first swimming legs subquadrate, 

 exopod nearly twice the length of the endopod; basal joint of the 

 exopod longer than the terminal; the two joints of the endopod the 

 same length. Second and third legs with two-jointed rami, which 

 are smaller than usual; spines confined to the tips of the terminal 

 joints; rami of the fourth legs apparently one-jointed, exopod only 

 with spines, endopod naked. 



Total length, 6.2 mm.; length of carapace on mid-line, 3 nmi.; 

 width of same, 3.7 mm.; combined length of dorsal plates on the 

 three thorax segments, 2 mm.; length of genital segment, 1.6 mm. 



Male. — Carapace a little longer than wide, including the posterior 

 lobes, ovate, the anterior portion considerably narrowed. 



Frontal plates narrow, closely compressed to the carapace, not 

 enlarged at the outer ends, but overlapping nearly the whole of the 

 basal joints of the first antennae as in the female. 



