PARASITIC COPEPODS — WILSON 565 



others. The 2 distal segments are reduced to mere rods curved into 

 a half circle and the margin of the cup, fringed with hairs, is in- 

 dented opposite each rod. The maxillipeds are stout with a wide 

 basal plate having a large raised area covered with hairs. The three 

 projections on the posterior margin of the plate are flat laminae 

 squarely truncated at their tips, the distal one nearly as wide as the 

 other two combined, the middle one narrow. The first and second 

 legs carry normal flagella ; in the fourth legs each basipod segment 

 has a laminate pad on its posterior margin. The one on the proximal 

 segment is almost squarely truncated, the one on the distal segment 

 is inclined outward and broadly rounded. All the legs are invisible 

 in dorsal view. Total length, 10 mm. Carapace width, 9.25 mm. 



Remarks. — This large Argulus has an almost perfectly circular 

 outline, the carapace covering everything except a part of the thorax 

 in the posterior sinus. The respiratory areas, the supporting ribs 

 of the sucking cups, and the posterior pads on the basipods of the 

 fourth legs furnish the best characteristics for identification. 



ARGULUS MELANOSTICTUS Wilson 



Plate 25, Figures 89-94 

 Argulus melanostictus Wilson, 1935, p. 776, pi. 25, figs. 1-4. 



A single female, U.S.N.M. No. 60504, was obtained by Dr. H. M. 

 Smith in plankton from the Gulf of Thailand. The host is unknown. 

 As this locality is separated by the entire width of the Pacific Ocean 

 from Monterey Bay on the coast of California, where the type speci- 

 mens were found, and as this female differs from the types in some 

 particulars it is here described and figured. 



FeTnale. — Carapace cordate, considerably narrowed anteriorly, 

 slightly longer than wide, the posterior lobes narrowly rounded, 

 strongly divergent and not quite reaching the fourth thoracic segment. 

 Cephalic area a little wider than long and projecting anteriorly; com- 

 pound eyes of medium size, far forward and well separated. The 

 entire dorsal surface of the carapace, the thorax, and the abdomen 

 are covered with small spots jet black in color. These spots are cir- 

 cular or slightly elliptical, vary considerably in size, and are not 

 arranged in any definite pattern (fig. 94). The first and second 

 segments of the thorax are equal in length, the third is longer and the 

 fourth shorter. The abdomen is two and a half times as long as wide, 

 the anal sinus extends beyond the center and the posterior lobes are 

 very narrow and acute. The caudal rami are very minute and basal 

 and partly concealed in dorsal view. The entire integument of the 

 abdomen, dorsal, lateral, and ventral, is raised into minute irregular 

 knobs like pebbled leather, which gives the wavy outline noticeable 

 in the figure. 



