no. 1404. PARASITIC COPEPODS—CALIGIDjE— WILSON. 533 



■KEY TO THE GENERA. 



1. First and fourth thoracic legs uniramose; second and third pairs hiramose 2. 



1. First legs only uniramose; second to fourth hiramose; frontal plates without 



lunules Calistes (Dana, 1852). 



I. Fourth legs only uniramose; first to third hiramose; no lunules; genital segment 

 with two horny, dentate processes, as in the genus Pandarus. 



Calina (van Beneden, 1892). 

 1. All four pairs of thoracic legs hiramose; rami two-jointed; no lunules. 



Dysgamus (Steenstrup and Lutken, 1861). 



2. Frontal plates provided with lunules; second maxilhe simple, spine-like 3. 



2. Frontal plates without lunules; second maxillae bifurcate or simple 7. 



3. Genital segment simple, without plates or processes, and not elongated. .4. 

 3. Genital segment without plates but prolonged posteriorly into processes 



nearly as long as the abdomen 6. 



3. Genital segment surrounded by a two-lobed membranous wing; abdomen 



with wings also Parapetalus (Steenstrup and Lutken, 1861). 



4. Free segment short; genital segment usually smaller, never much larger, than 



carapace, and flattened 5. 



4. Free segment produced into a long neck; genital segment many times larger than 



carapace, cylindrical Echetus (Kroyer, 1863), p. 611. 



5. Fourth legs normal; furca and first maxilla? present and well defined. 



Caligus (Midler, 1785), p. 555. 

 5. Both furca and first maxilla^ wanting; host, the mollusk Nautilus. 



subgenus. .Anchicaligus (Stebbing, 1901). 

 5. Fourth legs rudimentary, consisting of basal joint only, no exopod. 



subgenus.. Pseudocaligus (A. Scott, 1901). 

 5. Carapace proportionally very small; genital segment elongated; abdomen 

 longer than rest of body; second maxillipeds large and massive. 



subgenus.. Scisenophilus (van Beneden, 1852). 

 6. Four of these processes; the free segment short. 



Synestius (Steenstrup and Lutken, 1861). 

 6. Only two processes; the free segment prolonged into an elongate neck. 



Caligodes (Heller, 1865), p. 608. 



7. ( ienital segment simple, without plates or processes 8. 



7. ( ienital segment without plates, but prolonged posteriorly into two processes twice 

 as long as the segment itself; second maxilhe simple; no furca. 



Diphyllogaster (Brian, 1899). 

 7. < ienital segment covered with a fused dorsal plate extending backward over part 



of tlie abdomen Homoiotes, new genus, p. 661. 



s. Carapace horizontal, Tint folded; abdomen normal. 



LepeophtJieirus (Nordmann, 1832), p. 615. 

 8. Carapace normal, not folded; abdomen entirely wanting. 



Anuretes (Heller, 1865), p. 647. 



8. Carapace deeply incised at the center anteriorly; the two sides folded 



together Hermilius (Heller, 1865). 



ONTOGENY. 



The life history of the various genera here included is practically 

 identical, so I'm- as it is known. The development of fcheeggup to the 

 time it is extruded has already been given, and we have seen that each 

 egg was fertilized as it passed out. 



