662 PROCEEDIXGS OF THE NATIONAL MUSEUM. vol. xxvin. 



other, backward, and in the adult females usually forward, until they 

 finall}" fuse into a single plate or lamina. 



The genital segment, seen from below, is about half the width of the 

 carapace, and is ovate in shape, narrowing rapidly toward the poste- 

 rior end. The sides are very evenly rounded and the dorsal lamina 

 which covers the entire upper surface projects considerably l)eyond th(> 

 lateral margins, and extends backward on either side of the abdomen 

 in a broad, flattened lobe. These lol^es are about one-third the width 

 of the lamina at the point where they arise and each is tipped with a 

 stout spine. The sinus between them is deep and almost a perfect 

 semicircle in outline, leaving exposed the terminal half of the abdomen. 

 This latter is small, only one-fourth the length of the genital segment, 

 and composed of a single joint. Its base is concealed beneath the pos- 

 terior edge of the dorsal lamina, which covers both the free and geni- 

 tal segments, and it tapers strongly posteriorly. It is tipped with a 

 pair of small and narrow anal laminae, which are well separated and 

 armed with short setfe. The Q.gg strings are a trifle wider than the 

 abdomen and aliout as long as the carapace; each contains from seventy 

 to eighty eggs. 



Of the appendages the first antenna? are large, more than half the 

 length of the frontal plates; the two joints are the same length, the 

 terminal one being narrow and club-shaped. 



The second pair are of medium size; the basal joint is not much 

 swollen and is furnished on its dorsal surface, at the inner corner of 

 the distal margin, with a circular plate covered with short and stiff 

 bristles. The terminal claw stands at right angles to the ])asal joint 

 and is sharply bent near its tip. 



The first maxilli© are small, slender, and strongly curved; the second 

 pair are also small and are cut beyond the center, the inner ])ranch 

 being considerably^ smaller than the outer one. The mandibles are 

 strongly curved at the tip, with about a dozen large serrate teeth along 

 the inner margin of the curve. The first maxillipeds have a small chitin 

 lamina inserted in the inner margin of the terminal joint near its cen- 

 ter. They terminate in three claws instead of the usual two; the 

 inner one is considerably longer than the two outer ones, which are 

 about the same length. The outer claw has a pectinate edge along its 

 outer margin. 



The second maxillipeds are small, the terminal claw not more than 

 a third the length of the basal joint, with a long and slender accessor}^ 

 spine inserted near its base. 



The furca is small, the l)ase longer than the l)ranches and somewdiat 

 swollen, with a large rectangular foramen. The branches are short, 

 well separated, a little divergent, and blunt at the tips. 



The first swinnning legs have a large plumose seta on the posterior 

 margin of the basal joint and a stout spine at its distal corner. There 



