COPEPODA FROM CHPtlSTMAS ISLAND. 187 



OlTHONA ATTENUATA, Sp. n. (PL XXX. figS. 3-7.) 



Female (fig. 5). — Length *88 mm.; cephalothorax *4 mm.; 

 abdomen (including Th. 5) "48 mm., proportional lengths of 

 abdominal segments and furca 16:8:8:6'5:8; f ureal rami long 

 and narrow, arrangement of setae as in 0. nana. Front of 

 cephalon (fig. 3) slightly produced but not pointed. 



1st antenna (fig. 4) reaches to the beginning of the genital 

 segment ; proportional lengths of joints : 



1 2 3 4 5 6 7 8 9 10_11 



1« 28 y 19 31 lU 10 8 8 11 9" 



Small spine on the end of the 3rd joint. 



2nd antenna comparatively large, of the usual structure. 



Mandible : 2nd basal with one stout terminal seta ; endopodite 

 large, rounded, with four setse ; exopodite with five setae. 



1st maxilla : structure not made out. 



2nd maxilla and maxillipede as in 0. nana. 



Swimming-feet (figs. 6, 7) with three-jointed exopodites and 

 endopodites ; exopodites of 1st to 3rd feet with 1.1.3 outer edge 

 spines ; exopodite of 4th foot with 1.1.2 outer edge spines ; 

 terminal spines of 2nd and 3rd feet shorter than the exopodites ; 

 short strong seta on the inner edge of the 1st joint of the ex- 

 opodites of the 2nd and 3rd feet, not seen on the 1st foot. 



5th feet of the usual form. 



This species is closely allied to 0. nana and differs mainly in 

 the long drawn-out abdomen and furca and in the longer 1st 

 antenna. 



A single specimen was found in the collection. 



OlTHONA SIMPLEX, sp. n. (PI. XXIX. figs. 10-14; PI. XXX. 

 figs. 1, 2.) 



Female (PI. XXIX. fig. 11).— Length •38--42 mm. ; cephalo- 

 thorax •24-"26 mm., abdomen (including Th. 5) "M-'lfi mm. 

 (PI. XXIX. fig. 12), proportional lengths of abdominal segments 

 and furca 7:21:9:7:3:7. Rostrum absent, front of cephalon 

 (PI. XXIX. fig. 1 0) rounded as in 0. nana. 



1st antenna (PL XXX. fig. 1) reaches to the beginning of the 

 2nd thoracic segment ; proportional lengths of joints : 



1 2 3 4 .5 '^ 7 8 9 10 11 



65948 11 4 11 5 8 5 



2nd antenna rather short and stout. 



Mandible, 1st maxilla, 2nd maxilla, and maxillipede as in 

 0. nana.^ 



1st foot (PL XXX. fig. 2) : exopodite three-jointed with 1.1.3 

 outer edge spines and 0.1.4 inner edge setae, terminal spine longer 

 than the exopodite ; endopodite two-jointed with . 5 inner edge 

 and . 1 outer edge setse ; process of the 2nd basal between the 

 exopodite and endopodite rather large and acute. 



13* 



