504 



PKOCEEDINGS OF THE NATIONAL, MUSEUM 



vor,. 88 



and the specimens labeled nattereri are really the same as these. No 

 respiratory areas have been figured for any of these. They are, 

 however, included in the present description. 



ARGULUS AMERICANUS Wilson 



Figure 38 



Argulus americanus Wn-SON, 1902, p. 718, pi. 21, pi. 26, figs. 84-86 ; 1904, p. 627, 

 figs. 1-21. 



Carapace about as wide as long, overlapping the abdomen in both 

 sexes, alae overlapping thorax and truncate on large females; 

 cephalic area prominent, sinuses not deep. Abdomen subtriangular, 

 about as wide as or wider anteriorly than the length; sinus one-fifth 

 to one-fourth length of abdomen, sides diverging, anal furcae subter- 

 minal and large. The respiratory areas are peculiar in that the 



papi//a 



Figure 38. — Argulus americanus: a, Male accessory organs of last three legs ; 6, ribs of 

 suction cups ; c, respiratory areas ; d, dorsal view of second male appendage. 



smaller is oblong and located in a notch in the larger one, mesially 

 and anterior to it (fig, 38, <?). Females have been reported up to 

 12 mm. and males of about the same size. 



Antennae deeply sunk into carapace, very characteristic since bases 

 of first antennae are usually prolonged mesially into a knob ; there is 

 an extra spine between that at the base of the first antennae and the 

 postantennal spine, making three pairs in a row. The lateral hook 

 is bent posteriorly; base of segment enlarged into an anterior knob, 

 rather than the usual more mesial one; ventral spine large; second 

 antennae with large spine at the base ; basal segments not very large, 

 others progressively smaller and armed with setae. 



Suction cups with rims supported by ribs composed of two or three 

 elongate rods, interior ones longer than outer (fig. 38, b). Second 



