NO. 1404. PARASITIC COPEPODS—CALIGIDyE—]VILSnX. 583 



KEY TO THE GENERA. 



I . First and fourth thoracic legs uniramose; sei-ond and third pairs biramose 2. 



1. Firnt legs only nniramose; second to fourth biramose; frontal plates without 



lunules CalidcK (Dana, 1852). 



I. Fourth legs only uniranidse; lirst to tliinl biramose; no Itmules; genital segment 

 with two horny, dentate jirocesses, as in the genus I'auddrns. 



Cedilla (van Beneden, 1.S92). 

 1. All four pairs of thorat-ic legs l)iramose; rami two-jointed; no lunules. 



Dysgamus (Steenstrup and Liitken, 1861). 

 2. Frontal plates provided with lunules; second maxilli^ simple, spine-like ?>. 



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



3. Genital segment simple, without i)lates or processes, and not elongated. .4. . 

 3. Genital segment without plates but prolonged posteriorly into processes 



nearly as long as the abilomen 6. 



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



with wings also Parajx'talxs (Steenstrup and Liitken, 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 EchctHi^ (Kroyer, 1863), ji. 611. 



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



C<(H(/us (Miiller, 1785), ]>. r>55. 

 5. Both furca and first maxilhe wanting; liost, tlie mollusk Ndutilus. 



subgenus. .Anchicdligns (Stebbing, 1901). 

 5. Fourth legs rudimentary, t'onsisting <if basal joint only, no exopod. 



i^uhgenus. . Pseudoccdigus {\. Scott, 1901). 



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



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



subgenus. .*SVv',T?io^;//(7».v (van Beneden, 1852). 

 6. Four of these i)rocesses; the free segment short. 



Sy7U'.'<t'nis (Steenstrup and Liitken, 1861). 

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



CaUgodes (Heller, 18t)5), p. 608. 



7. Genital segment simjile, without plates or proce.sses 8. 



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

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



Dlphgllogaster (Brian, 1899). 

 7. (ienital segment covered with a fused dorsal ])lale extending backward over part 



of the abdomen Ilomoiotes, new genus, \). 661 . 



8. Carapace horizontal, not folded; abdomen normal. 



Lepi'opJdJieinis (Nordmann, 1832), p. (il'i. 

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



Aiuirett's (Heller, 1865), p. 647. 



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



together IL'niiiliim (Heller, 1865). 



ONTOGENY. 



The life history of the various genera here inchided is practically 

 identical, so far as it is known. The development of the egg- up to tlu^ 

 time it is extruded has alread}^ been given, and we have seen that each 

 egg was fertilized as it passed out. 



