COPEPODA 



787 



fined to a single species of fish for a host, hut seem ahlc to make 

 use of a great variety, and may even attach themselves to other 

 aquatic animals, Hke tadpoles. Some of them can live almovi 

 equally well in both salt and fresh water. 



The following key to the species of Ar^uhis which Im-, 

 described from the fresh waters of America is adapted from \Vi 

 paper on the Argulidae. 





KEY TO NORTH AMERICAN FRESII-WATKR Akc.l LII)\L 



1 (4, 9) Carapace lobes overlap base of abdomen. 



2 (3) Diameter of sucking disks 0.25 mm. 



Arguliis catoslomi Dana and llirnclt 



Spines on antennae rcduccH in number, small and mrak'. 

 abdomen small and orbicular; found on »u<k«T. Catoti^ 

 mus commersoni, and chub sucker, Lrtmysam imtfUj »^ 



longus. 



FiC. 1241. Argulus catoitomi- lAficr Wi 



3 (2) Diameter of sucking disks 0.15 mm 



Argulus amfricanus Wilson i<x>v 



Spines on antennae large and strong, reenforced; abdomen large and broadly cordate. Found 

 on mudfish, Amia calva. 



4 (i, 9) Carapace lobes just reach base of abdomen 5 



5 (8) Carapace orbicular, wider than long 6 



6 (7) Anal sinus narrow and slit-like. A rgulus versicolor Wilson i (X>3 . male. 



7 (6) Anal sinus broadly triangular. . .Ir^w/wj macuhsus Wilson IQ03. 

 Anal papiUae lateral; bases of antennae widely scparate.l; found upon the mUKaUoOft, 



Lucius masquinongy . 



8(5) Carapace orbicular, longer than wide. 



Argulus dppcwiv U'.>^U^ \\ \\'>^M\ x-. 

 Found upon a sucker. 

 9(1,4) Carapace lobes do not reach abdomen 



10 (16) Swimming legs with flagclla 



11 (13) Carapace orbicular, wider than long 



10 

 1 1 



