NO. 1504. 



AMERICAN PARASITIC COPEPODS— WILSON. 



678 



long, evenly rounded anteriorly, slig-htly iiurrovYod and emarginate pos- 

 teriorly. The dorsal surface of this cai-apace shows no grooves at all, 

 which would naturally be expected since there is no fusion as yet be- 

 tween tlie head and thorax, neither have the segments formed any 

 lobes or pro(;esses. 



Frontal platessmall but distinct; antennre slender but proportionally 

 long, their tips reaching 

 beyond the lateral margins 

 of the carapace. Eyes 

 small, some little distance 

 apart on either side of the 

 mid-line and just in front 

 of the center of the cara- 

 pace. This separation of 

 the eyes from the earliest 

 known stage is a notable 

 departure from the condi- 

 tion in the Caligina?. In 

 the lattertheeyesare fused 

 from the beginning of the 

 metanauplius stage '^. In- 

 deed in the preceding nau- 

 plius stage whenever the 

 eyes are visible they are 

 fused on the mid-line^. 

 This suggests that the 

 characteristic median eye 

 of the nauplius larva may 

 be a more complete fusion 

 of two e3'es. 



The first three segments 

 of the thorax are free, of 

 about the same length, but 

 diminish a little in width 

 from in front backward. 



The first one is the same 

 width as the carapace, and 

 each of the three carries a 

 pair of more or less rudi- 

 nientar}' swimming legs. 

 Kroyer representsall three 

 pairs as uniramose, the first and third pairs two-jointed, the second 

 pair three-jointed. 



He saj's nothing about these swimming legs in the text, so that we 



0'25inm. 



Fig. 1.— Chalimus of Trebius caudatus (aktkr kroyer). 



«Proc. U. S. Nat. Mus., XXVIll, 1905, p. 541, fig. 

 Proc. N. M. vol. xxxi— 06 44 



40. 



'' Idem, fig. 39. 



