NO. 1788. NORTH AMERICAN ERGA8ILID/E— WILSON. 369 



sented by the figures 11, 5, 4, 6, and 2. Genital segment narrower 

 than the fifth segment, with nearly straight sides and short evenly 

 rounded lobes at the posterior corners. From the center of each lobe 

 on the ventral surface projects a single short spine, while from tlie 

 angle between the lobe and the first abdomen segment projects a short 

 finger-like process, curved slightly outward. Abdomen three-jointed, 

 tapering posteriorly, the first segment as long as the other two and 

 twice the width of the terminal segment. Anal laminsB as long as the 

 last segment, inclined toward each other, and each armed with a single 

 stout seta at the tip, twice as long as the entire abdomen, a very short 

 seta on either side of it, and a slightly longer one on the outer margin 

 near the base. 



Egg-cases ellipsoidal, half as long as the entire body, and narrowed 

 a little at either end; eggs arranged in six or eight longitudinal rows, 

 about eighteen in the longest central rows. 



First antennse showing the joints distinctly, the fused basal joints 

 with a fringe of heavy setie around the anterior margin and running 

 back on the dorsal surface of the third joint to the posterior margin, 

 the last seta projecting diagonally baclavard from the posterior corner 

 of the third joint and considerably longer than the others. From the 

 anterior margin of the second joint project a pair of tactile hairs 

 nearly three times the length of the setse (fig. G). 



Second antenna? of the usual pattern, the terminal joint ending in 

 two long curved claws of about the same size, and a finger-like process 

 covered with short spines. 



Labrum two-fifths wider than long, narrowed into a knob on either 

 lateral margin. Mandible long, smooth, and slender, directed diago- 

 nally backward along the margin of the labrum. 



First maxillae small, each armed with two short and nearly parallel 

 setae. Second maxilla long and slender, the terminal joint simple, 

 covered v»'ith short hairs and directed slightly forward, almost meet- 

 ing the tip of the mandible. 



Maxiiliped very large, the basal joint distinctly visible, showing 

 even the musculature, and extending laterally far outside of the 

 other mouth-parts. Second joint turned forward and inward and 

 about tlic same size as the basal joint, with a single large plumose 

 seta at the tip on the ventral surface, alongside the terminal claw. 

 The latter is stout but short, not reaching the middle of the second 

 joint, and with a simple crescentic curve, the outer convex margin 

 of which is broken at the center by an angular protuberance. 



Swimming legs of the usual form, each ramus of the first pair two- 

 jointed, the terminal joint of the exopod with ten setae, covering its 

 entire margin, the basal joint unarmed. The terminal joint of the 

 endopod carries six large setae, the basal joint one on the inner margin. 



Froc.N.M.vol.39— 10 26 



