COPEPODA FROM IFALUK ATOLL 291 



Orthopsylliis agnathus Klie, 1950 



Orthopsyllus agnathus Klie, 1950, p. 108, figs. 129-133.— Noodt, 1955, pp. 82, 83.— 

 Roe, 1958, p. 231; 1960, p. 283. 



Originally described from Helgoland in Germany (Klie, 1950). 

 9 1.15 mm., cf 1 mm. Later recorded from the Dalkey area of County 

 Dublin and Lough Ine of County Cork in Ireland (Roe, 1958, 1960). 



Orthopsyllus psammophihis Noodt, 1955a 



Orthopsyllus psammophilus Noodt, 1955a, p. 208, figs. 9-23; 1958, p. 81. 



This very characteristic species was described by Noodt from 

 interstitial water of sandy beaches at Teneriffe in the Canary Islands, 

 where the species, which shows many adaptations to its peculiar 

 mode of life, appears to be fairly common. It occupies a more or 

 less isolated position among the remaining species of this genus, 

 which generally live between algae, roots of laminarians, etc. It has 

 not been recorded from other localities. 9 0.52-0.57 mm.; cf 0.51-53 

 mm. 



Orthopsyllus dubius, new species 



Figures 114e-i, 115a,6 



Material. — Loc. 594, 1 ad. cf, 0.56 mm. 



Description. — The following is based on the above-mentioned 

 specimen (holotype), which has been dissected and mounted. 



Adult male, total length 0.56 mm.; greatest diameter 0.11 mm.; 

 length of longest f ureal seta 0.21 mm. 



Body slender, cylindrical, greatest diameter at end of cephalic 

 somite and very gradually tapering posteriorly. Frontal part of 

 head also narro\ving and at once remarkable by great development 

 of rostrum (fig. 115b). No distinction between cephalothorax and 

 abdomen; various somites of body stand out clearly because of cir- 

 cular constrictions of anterior parts of somites. Head and 1st thoracic 

 somite fused to form cephalic somite, which, without rostrum, is as 

 long as combined lengths of thoracic somites 2 to 4. Back almost 

 straight, with small depression opposite oral aperture; sides mod- 

 erately produced and rounded; oral field produced, in lateral view 

 distinctly visible (fig. 115a). Rostrum notably big, plate-shaped, 

 separated from head by shallow groove, as long as combined length 

 of antennular segments 1 and 2, curving very slightly downward. 

 Apex triangularly produced, extreme tip rounded. There is an 

 incision on each side, carrjdng a fine hair of the frontal organ. 



All somites of the body have about the same length, with the 

 exception of the 4th thoracic and the anal somites, which are slightly 

 longer. Anal somite slightly wider than long, with broadly rounded 

 anal plate, placed at distal end of somite. All somites distally 



