NO. 1504. AMERICAN PARASITIC COPEPODS— WILSON. 711 



Anal laiiiinte .short and wide, each bearing four large and one small 

 plumose setae. 



First antennae two-jointed, the second joint terminating in very long 

 nonplumose setfe, which are dichotomously branched toward their tips. 

 Second antennae much enlarged and curved over ventrally in a half 

 circle. They are the chief organs of prehension and are carried 

 straight forward side by side in front of the carapace. 



Second maxilla? with distinct endopod and exopod, both of which 

 are bifurcate at their tips. First and second maxillipeds two-jointed 

 and extending well be3"ond the lateral margins of the carapace. Two 

 pairs of swimming legs, each biramose, the rami one-jointed. 



Total length, including second antennae, 1.15 mm.; length of cara- 

 pace, 0.65 mm.; width of same, 0.32 mm.; width of free segments, 

 0.15 mm. 



Color as in the adult, with pigment spots only along the posterior 

 margin of the carapace and on the abdomen. 



Chalhnus (figs. 10-15). — One thorax segment united with the head 

 to form the carapace, which is elliptical, about one-half longer than 

 wide, the posterior border emarginate. Frontal plates well defined 

 and projecting on either side over the basal joints of the first antenna. 

 Eyes farther forward than in the metanauplius, but still very large. 

 Second and third segments fused intei' se, the former much wider than 

 the latter. 



Fourth and genital segments still fused with the abdomen, but much 

 longer than in the metanauplius and showing a deep constriction on 

 either side. Appendages as before, but each first antenna is now tipped 

 with five short and simple setae; the exopods of the second maxillae are 

 now reduced to papillw on the bases of the endopods, and there are 

 three pairs of swimming legs all biramose and the rami one-jointed. 



Total length 2 mm., length of carapace 1 mm.; width of the same 

 0.7 mm. ; width of first free segment 0.55 mm, ; of the second, 0.35 mm. 



Pigment spots now distributed along the entire length of the lateral 

 margins. Otherwise colored like metanauplius. 



This is a large and clean-looking species and must be fairly common 

 since the United States National Museum collection contains the fol- 

 lowing lots of specimens: From the smooth dog-fish, Mustelas cavis 

 (Cat. No. 8123, U.S.N. M.), consisting of twelve females and six males, 

 taken as the types; (Cat. No. 32830, U.S.N.M.), a single male; (Cat. 

 No. 32831, U.S.N.M.), three females; (Cat. No. 32832, U.S.N. M.), eight 

 females; 6204, one female from Long Island Sound; 32833, one female; 

 (Cat. Nos. 32834 and 32835, U.S.N.M.), development stages, ten speci- 

 mens each; (Cat. No. 32836, U.S.N.M.), tvvo females; (Cat. No. 32837, 

 U.S.N.M.), five females. From Squalus acanthias^ three females, two 

 males; from sand shark, Emjompodus littoralh^ three females, both 

 by V. N. Edwards, the former 32838, the latter 61(»2. From barn- 



