398 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 115 



Mesometopa sinuata, new species 



Figure 4 



Male. — Head not as long as first 2 body segments combined; 

 rostrum short, triangular from above; lateral lobes triangular; eye 

 small, oval; epistome very prominent, deeply cleft (fig. 46). Antenna 

 1 about }i length of body, peduncle rather stout, first joint longer than 

 second and third combined, flagellum shorter than peduncle and 

 composed of 10 or 11 joints, each of which bears sensory filaments on 

 lower distal corner. Antenna 2 much longer than antenna 1, third 

 joint ji length of fourth, which is as long as fifth; flagellum slightly 

 shorter than fifth peduncular joint and composed of 1 long and 4 

 shorter joints. 



Mandible, cutting-edge, and accessory plate toothed, 7-8 spines in 

 spine row, palp small, consisting of basal joint bearing lateral spine, and 

 smaller conical second joint bearing apical spine (fig. id). Maxilla 1, 

 inner plate without setae, outer plate with 5 large, 1 small spine, palp 

 1-jointed, bearing 7 terminal spines. Maxilliped, inner plate not 

 reaching to base of first joint of palp; outer plate consisting of only 

 short triangular extension of inner margin of third peduncular joint; 

 palp long, slender, fourth joint with very fine teeth on inner margin. 



Gnathopod 1 rather short, slender; second joint very slightly ex- 

 panded; fourth joint reaching to about middle of fifth; fifth joint as 

 long as, but wider than, sixth; sixth joint with front and hind margins 

 slightly convex, palm very oblique, convex, armed throughout with 

 fine sharp teeth, few slender spinules, and defined by group of spines; 

 seventh joint fitting palm, bearing on inner margin row of fine spinules, 

 and small forward-pointing tooth near apex (fig. Ag). Gnathopod 2 

 with outside front margin of second joint expanded into thin trans- 

 parent lobe on outer and inner front margin; fourth joint with tri- 

 angular lobe on inside surface projecting above upper margin of fifth 

 joint, lower margin of joint produced forward on outside of lobe of 

 fifth joint; fifth joint normal; sixth joint large, longer than wide, palm 

 very oblique with deep oblong sinus between defining tooth and distal 

 portion of palm, which is provided with several blunt teeth and few 

 setules (fig. 4:h) ; seventh joint stout, curved, shorter than palm and 

 bearing closely set setae on inner margin and a few setae on outer 

 margin. 



Pereopods 1 and 2 about equal in length, but 2 stouter; fourth 

 joint with front margin produced slightly downward. Pereopod 1 

 almost entirely devoid of spines. Pereopods 3-5 consecutively shorter. 

 Pereopod 4, second joint linear; fourth joint expanded with lower 

 hind corner reaching to about middle of fifth joint; fifth joint shorter 

 than sixth; seventh joint over % length of sixth. Pereopod 5, second 



