COPEPODA FROM IFALUK ATOLL. 287 



synonym of Orthopsyllus. K. improportionatus very probably is 

 identical with 0. linearis. Jakobi apparently overlooked the small 

 1st endopodal segments of legs 2 and 3, which has put him on the 

 wrong track. All information given about his new species (with the 

 exception of the endopodites of legs 2 and 3) supports this view. 

 The number of species lately has increased considerably, as evident in 

 the following list, but the variability'- of the type species, 0. linearis, 

 which has a very wide distribution, is still insufficiently known. 

 It seems probable, therefore, that some of the species of the list will 

 sooner or later sink into the synonymy of 0. linearis, particularly 0. 

 major Klie, 1939, and 0. agnathus Klie, 1950. Klie, who considered 0. 

 linearis an uncertain species, failed to indicate differences between his 

 new forms and the type species. Authors who subsequently recorded 

 Klie's species apparently had no difficulty in recognizing these forms 

 but failed to indicate on what grounds they reached their decisions. I 

 am not particularlj- impressed by the characters which Noodt (1955) 

 uses to discriminate between his form bulbusus of 0. linearis and 

 the type species, 0. agnathus, and 0. major; the sexual dimorphism 

 in this form apparently is much more pronounced than in the typical 

 0. linearis. 

 List of the species of Orthopsyllus Brady and Robertson, 1873: 



Females Males 



Lilljeborgia linearis Claus, 1866 L. linearis Claus, 1866 



{ = Katacletodes improporiionaius Jakobi, 1954) 

 Orthopsyllus linearis f . bulbosus Noodt, 0. linearis f. bulbosus Noodt, 1955 



1955 

 0. propinquus Monard, 1926b 0. propinquus Monard, 1926b 



0. wallini Lang, 1934 0. wallini Lang, 1934 



0. major Klie, 1939 O. major Klie, 1939 



O. spec. Sewell, 1940 

 0. rugosus NichoUs, 1941 

 O. sarsi Klie, 1941 0. sarsi Klie, 1941 



( = 0. linearis G. O. Sars, 1909, not Claus) 

 0. litloralis NichoUs, 1942a 0. liitoralis NichoUs, 1942a 



0. similis NichoUs, 1942a 0. similis NichoUs, 1942a 



0. agnathus Klie, 1950 O. agnathus KUe, 1950 



0. psammophilus Noodt, 1955a 0. psammophilus Noodt, 1955a 



0. dubius, new species 

 0. pectinicauda, new species 0. pectinicauda, new species 



Key to the Females of Orthopsyllus 



1. Body compressed dorsoventrally. 1st antennular segment with short ex- 

 ternal spine, 2nd segment without spine. Internal furcal corner produced 

 to a short spine. 2 of furcal setae thickened, internal with thickened 

 base terminating in fine filament; external a short spine. Exopodite and 

 baso-endopodite of leg 5 fused O. psainmophilus Noodt 



