PARASITIC COPEPODS — WILSON 569 



dal rami. The testimony of the structural characters of the append- 

 ages is even more decisive. Figures 7 and 8 show the two pairs of 

 antennae, the spines on the basal segments in stizostethii large, long, 

 and pointed (fig. 7), those in canadensis smaller, short, and blunt 

 (fig. 8) . Figures 9 and 10 show the supporting rods of the two species, 

 the segments in canadensis (fig. 10) doubly imbricated and strongly 

 tapered, those in stizostethii (fig. 9) simply imbricated and much less 

 tapered. Figures 11 to 14 show the accessory sexual characters of 

 the third and fourth legs of the respective males. The prominent 

 curved spine on the posterior margin of the third basipod in canadensis 

 (fig. 12) and the two knobs at the anterior distal corner of the fourth 

 basipod (fig. 14) contrast strongly with what is found in the same 

 localities in stizostethii. Such a comparison can prove only that cana- 

 densis is a perfectly valid species and not a synonym of stizostethii. 

 In support of this statement it may be noted that the hosts of canadensis 

 belong almost exclusively to fish of the salmon and trout families 

 while the hosts of stizostethii are found in the sauger and pike families. 



ARGULUS NIGER WUson 



Plate 20, Figukes 15, 17 



Argulus niger Wilson, 1902, p. 714, pi. 18, figs. 42^5. 

 Argulus pugettensis Meehean, 1940, p. 487 (part). 



Meehean expresses the opinion (1940, p. 467) that "The male of A. 

 niger has never been described, since it is the same as pugettensis ex- 

 cept that the former is very dark, as its name indicates." If the lack 

 of a male is to be taken as evidence that the female must become the 

 synonym of some other species whose male is known, the number of 

 copepod species would be greatly diminished. The same statement is 

 made by Meehean (1940, p. 468) in reference to A. latus Smith, but 

 the male of that species was found among the specimens here identified 

 and is fully described on p. 560. There is a similar chance that the 

 male of niger will be found some day among parasitic copepods from 

 the Pacific coast. 



Following his redescription of pugettensis Meehean remarks (1940, 

 p. 489) : "As far as can be determined niger is identical in every re- 

 spect." Meehean himself notes the difference in color, which in the 

 present instance is an exceptional one. Ordinarily the color of pre- 

 served specimens is not worth recording although in the living animal 

 it presents one of the most important specific distinctions ; but black 

 is an exceedingly rare color in parasitic copepods and may well serve 

 as the first character to separate niger from pugettensis. Figures 15 

 and 16 show the antennae of the two species and figures 17 and 18 the 

 maxillipeds. A cursory examination of these figures will be sufficient 



558871—44 6 



