NO. 1573. PA njSITIC COPEPODS— WILSOX. 471 



dorsal surface of the genital segment. The anterior ventral surface 

 of the abdomen and the edges of the dorsal plates of the genital seg- 

 ment have a few spots of light brown pigment. 



Egg masses a deep orange brown. 



Male. — Carapace similar to that of the female, and with the same 

 grooving on its dorsal surface. The cephalic and thoracic portions 

 of the lateral areas do not differ as much in size as in the other sex, 

 and the posterior sinus is rather deej)er. The lateral lobes on the 

 second segment and the dorsal plates on the third and fourth seg- 

 ments correspond closely with those in the female, the last men- 

 tioned covering the whole of the genital segment and the most of the 

 the abdomen. 



Genital segment transverseh" elliptical, nearly twice as wide as 

 long, narrowed into a neck where it joins the fourth segment. 



Abdomen also transversely elliptical and terminal, a little more 

 than half the diameter, but nmch less than half the length of the gen- 

 ital segment. Anal laminte terminal, small, and close to the anus on 

 either side; the setse which they carry are plumose, but rudimentary. 

 Appendages similar to those of the female, with the usual sex dis- 

 tinctions manifested m the larger size of the second antenna^, ma5c- 

 illae, and second maxillipeds, and in an increase in the number and 

 length of tlie ])lumose seta^ on the swimming legs. The fourth legs 

 have large lannnate l)asal joints and one-jointed rami, but there is 

 no fold of skin in the basal joints, and the rami are not as large and 

 rudimentary as in the female. The testes are large and very appar- 

 ent in well-preserved specimens; the spermatophore receptacles in 

 the genital segment are circular in outline and so large as to nearly 

 fill the entire segment. 



Total length, 14 to 17 mm.; length of carapace on mid-line, 8 

 mm. ; width of same, 1 1 mm. ; length of fourth segment plates, 4 mm. ; 

 width of same, 6 mm.; length of genital segment, 3 nun.; of the 

 abdomen, 1.8 mm. 



Color as in the female, but rather lighter and more transparent, 

 and without pigment spots on the ventral surface. 



(latreillii, in honor of Pierre Andre Latreille.) 



The U. S. National Museum collection contains three lots of this 

 species, all from the gills of Mola mola: one taken at Woods Hole, 

 Cat. No. 6017, U.S.N.M., contains females only; the second, also 

 taken at Woods Hole, and Cat. No. 32796, U.S.N.M., contains both 

 sexes; the third was taken by the Fisheries steamer Albatross on the 

 Pacific coast at Station 4345, and is Cat. No. 32797, U.S.N.M.; it 

 also contains both sexes. 



