KEY TO THE COMMON GENERA OF COPEPODS 



1. Parasitic, usually on the gills of fish; mouth appendages adapted for suck' 



ing; body segments often reduced 2. 



Free-swimming; mouth appendages adapted for chewing; with five or six 



segments in the cephalothorax and three to five segments in the ab' 



domen 5. 



2. Body flattened, covered with a disc-shaped or oval carapace; no egg sacs; 



with a pair of compound eyes; Family Argnlidae 

 Argulus Miiller 

 Body usually more cylindrical or sac- like; females with egg sacs 3. 



3. Body resembling the free swimming Copepods; Family Ergasilidae 



Ergasilus Nordmann 

 Body more worm-like or sac-like, more or less unsegmented or with the 

 legs minute or absent 4. 



4. Usually with about four pairs of minute swimming legs; Family Lernaei' 



dae 



Lernaea Linn. 

 With one or two pairs of minute legs or legs absent; Family Lernaeopodi' 

 dae 



Salmincola Wilson 

 (Lernaeopoda Nordmann (part) ) 



5. First antennae about as long as the body, of twenty or more segments 6. 

 First antennae not longer than the cep^lothorax, of eighteen or less seg- 

 ments 9. 



6. Endopodite (inner branch) of first pair of feet of only one segment; 



Family Temoridae 



Epischura Forbes 

 Endopodite of first pair of feet of two or three segments 7. 



7. Endopodite of first pair of feet of two segments; Family Diaptomidae 



Diaptomus Westwood 

 Endopodite of first pair of feet of three segments; Family Centra pagidae 



8. 



8. With twenty-three or twenty-four segments in antennae 



Osphranticum Forbes 

 With twenty-five segments in antennae 

 Lwinocalanus Sars 



9. With seven or eight segments in first antennae; cephalothorax and ab- 



domen about the same width; Family Canthocamptidae 10. 



With ten to seventeen segments in first antennae; abdomen distinctly 



and suddenly narrower than the cephalothorax; Family Cyclopidae 11. 



10. With two segments in the small branch of the second antenna 



Canthocamptus Westwood 

 With one segment in the small branch of the second antenna 

 Attheyella Brady 



11. With ten to tvv'elve segments in the first antennae 12. 

 With seventeen segments in the first antennae 13. 



186 



