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PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 88 



rior surface; distal end of coxa has a larger papilla parallel to that 

 of the basis so that there appear to be two ridges across the anterior 

 side near the origin of the rami ; the coxa is widened somewhat to a 

 point near the middle, but no enlargement is formed for the socket. 

 The socket consists of a shallow groove running dorsolaterally from 

 the middle of the segment to a point just below the large papilla 

 with the deepest part farthest inward. On the fourth appendages 

 the peg is placed on the distal edge of the basis near the origin of 

 the exopod as a slight fingerlike papilla with the tip turned mesially, 

 a second mesial papilla bends outward to meet it. The usual chiti- 

 nous ridge runs obliquely around the base; natatory lobe is much 

 reduced. The exopod is attached to the basis by a bent kneelike por- 

 tion, thus separating the two rami considerably. 



FiGDRB 22.- 



-Argulus stisostethii: a. Respiratory areas ; h, ribs of suction cups ; c, male 

 accessory organs of second, third, and fourth legs. 



Females have been reported to 12 mm. and males to 8.5 mm. They 

 have been reported from the wall-eyed pike {Stizostedion vitreum)^ 

 Niagara River, Buffalo, N. Y. ; Cynoperca canadensis^ Fairport, Iowa ; 

 Coregonus and Acipenser fulvescens, Le Claire, Minn.; brook trout, 

 stickle-backs, perch, and suckers, Cape Breton Island, New Bruns- 

 wick; Esox mmquinongy^ Vilas County, Wis.; skin of salmon, St. 

 John, New Brunswick ; swimming in Lake Erie. 



The only difference that could be noted between stizostethii and 

 caivadensis is a slight variation in size and shape of body and some 

 structures. These were no greater than variations within the species. 

 There is some tendency for the occurrence of aberrant types of ex- 

 ternal respiratory areas in some specimens. 



