568 PROCEEDINGS OF THE NATIONAL MUSEUM vol. m 



ARGULUS BIRAMOSUS Bere 



Plate 20, Figures 2, 4, 6 



ArgulU'S hiratnosus Bere, 1931, p. 428, pi. 9, figs. 1-7. 

 Argulus appcndiculosus Meehean, 1940, p. 512 (part). 



There is considerable similarity between hirajnosus and appcn- 

 diculosus in the respiratory areas and supporting rods (figs. 3 and 4), 

 but there is no real identity, as Meehean claims. There are many 

 differences in the structural characters of the various appendages. 

 The second segment of the first antenna in appcndiculosus is armed 

 with a spine on the ventral surface near the proximal end and two 

 transverse ridges at the distal end across the base of the lateral claw 

 (fig. 1). Both spine and ridges are absent in l}iramosus (fig. 2). The 

 flagellum is biramose in both species but it differs in shape and arma- 

 ture. The second antennae are 4-segmented in appcndiculosus^ the 

 basal segment without setae. In hirainosus they are 5-segmented, 

 every segment armed with setae. 



Meehean's description of the abdomen as spindle-shaped applies 

 better to hiramosus than to appcndiculosus^ where it is scarcely nar- 

 rowed at all anteriorly ; cordate would be a more accurate term. In 

 the latter species the caudal rami are lateral, close to the base of the 

 posterior sinus, and practically invisible dorsally. In hiramosus 

 they are farther from the base, stand out prominently in dorsal view, 

 are divergent, very much larger, and truncate at their tips. Meehean's 

 description fits them admirably but does not apply at all to the caudal 

 rami of appcndiculosus (figs. 5, 6). 



These differences may not be enough fully to establish hiramosus 

 as a valid species, but they are more than enough to question the 

 validity of this species as a synonym of appcndiculosus. Unfortu- 

 nately, Dr. Bere did not have a male in material that was collected at 

 Trout Lake, Wis., and one must be examined before synonymy can be 

 finally settled. In the meantime Argulus hiramosus should stand. 



ARGULUS CANADENSIS Wilson 



Plate 20, Figures 8, 10, 12, 14 



Argulus canadensis Wilson, 1916, p. 348, pi. 60, figs. 1-6 ; 1936c, p. 355, figs. 1-9. 

 Argulus stisostethii Meehean, 1940, p. 479 (part). 



Despite the statement that this species is the same as stisostethii 

 Kellicott, Meehean (1940, p. 480) admits "a slight variation in size 

 and shape of body and some structures." The difference in size ap- 

 plies to nearly all the specimens and the variation in shape is seen 

 especially in the cephalic area of the carapace, the position of the 

 compound eyes, the formation by the dorsal ribs of the carapace of 

 a definite shoulder on either side of the cephalic area in canadensis 

 and its complete absence in stisostethii, and in the position of the cau- 



