646 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvm. 



indication of jointing in these appendages. We thus have here a 

 form in which the fifth legs are less rudimentary than usual, and one 

 which leaves no possible doubt as to their morphological significance. 



LEPEOPHTHEIRUS ROBUSTUS Kroyer. 



Plate XXV, figs. 314, 315. 



Lepeophtheirus robustus Kroyer, 1863, p. 135, pi. vi, fig. 6 a-c. — Bassett-Smith, 

 1899, p. 456. 



Male. — Carapace longer than the rest of the bod}^ the proportion 

 about 5 to 2 and strongly arched. Frontal plates weakly developed 

 and not very distinct. Free segment quadrangular in form with 

 rounded corners, a little contracted anteriorly. 



Genital segment about one-fourth as long as the carapace, and of 

 the same width and length. On either side anteriorly there is a fold 

 of skin which fills up the space between this segment and the one in 

 front of it. The posterior corners are squarely rounded and the fifth 

 legs appear as stout pointed knobs armed with three or four long seta?. 



The abdomen is half as long as the genital segment and of about the 

 same width and length. The anal lamina? are one-fourth as long as 

 the abdomen and a little wider than long. Thej 7 are armed with seta? 

 which are at least four times as long as they are themselves, and with 

 tufts of hair on either side at the base of the seta?. 



The first antennae are short, with the basal joint somewhat plump 

 and longer than the second joint. In the second antenna? the terminal 

 claw is particularly long and sharp. 



The first maxilla? are quite stout, while the second are larger still, 

 and are deeply cleft at the tip into two acuminate branches. The 

 proboscis is plump, not quite twice as long as wide. The first maxilli- 

 peds are weak, the inner terminal claw fully twice as long as the outer. 

 The second pair are proportionally larger but with a short terminal 

 claw. 



Furca small and somewhat difficult to see; base longer than the 

 branches, squarely truncated anteriorty, with a slender frame and a 

 large, half -moon-shaped foramen. The branches are short and plump 

 and cleft at the ends; the secondary branches are very shoirt, the outer 

 one much wider than the inner, and turned outward, white the inner 

 one points straight backward. ft 



First swimming legs short and stout, the second joint plump and 

 egg-shaped, with a spine and a rounded protuberance on its anterior 

 border. Second swimming legs characterized by their stoutness; 

 rami of the third legs small and close together. Fourth legs small but 

 stout, four-jointed, with the basal joint as long as the other three; the 

 latter decrease regularly in size in the proportion of 4, 3, and 2. 

 There are only four spines, the second joint ending in an enlarged and 



