186 MR, G. P. FARRAN ON 



thorax '48 mm.; abdomen (including Th. 5) -42 mm. ; proportional 

 lengths of abdominal segments and furca 9 : 20 : 9 : 9 : 8 : 6. 



Rostrum (PI. XXVIII. fig. 1) pointed, not visible in dorsal 

 view, similar to that of 0. siiiiilis and 0. clecijneKS. 



1st antenna reaches to the beginning of the genital segment ; 

 proportional lengths of joints : 



1 2 3 4 5 6 7 8 9 



(24+28; (4+rz) (16+16) 40 (20 + 20+2U+ 5i2) (16 + 38) 14 16 20' 



the first three and the 5th and 6th joints being svibdivided by 

 imperfect jointing in the proportions indicated. 



2nd antenna slightly lai'ger comparatively than in 0. decijrlens. 



Mandible (PI. XXVIII. fig. 2) : endopodite with four setfe. 



1st maxilla : exopodite with three modei-ately strong terminal 

 setas, endopodite with one small seta. 



2nd maxilla and maxillipede of the usual type. 



1st foot (PI. XXVII. fig. 9) : exopodite with 1.1.2 outer edge 

 spines and 0.1.4 inner edge setfe, terminal spine shorter than 

 the exopodite ; endopodite two-jointed with 1 . 5 inner edge and 

 1 outer edge setfe. 



2nd foot (PI. XXVII. fig. 10) : exopodite with 1,0.2 outer 

 edge spines and 1.1.5 inner edge setae ; the inner edge seta on 

 the 1st joint is small ; terminal spine approximately equal to the 

 exopodite : there is a small tooth on the outer edge of the 3rd 

 joint of the exopodite proximal to the first spine ; endopodite 

 with 1,2.4 inner edge and 1 outer edge setfe, 



3rd foot (PI, XXVII, fig. 11): exopodite with 1,0,1 outer 

 edge spines and 1,1,5 inner edge setfe, inner edge seta on 1st 

 joint gmall ; there is a small tooth in the middle of the outer 

 edge of the 3rd joint ; terminal spine slightly longer than the 

 exopodite. 



4th foot (PI XXVII. fig. 12): exopodite with 0.0.0 outer 

 edge spines and 1.1.5 inner edge setae, inner edge seta on 

 1st joint small ; terminal spine slightly longer than the exopodite ; 

 endopodite with 1,2,3 inner edge and 1 outer edge setfe. 



There is a well-developed outer edge seta on the 2nd basals of 

 all the swimming-feet and an inner edge seta on the 1st basals, 



5th feet of usual form. 



This species, like 0. decijnens, can with difiiculty be dis- 

 tinguished from 0. similis without examination of the swimming- 

 feet. The shorter terminal spines and the presence of two outer 

 edge spines on the 3rd joint of the exopodite of the 2nd foot and 

 of a small inner edge seta on the Lst joints of the 2nd to 4tb. 

 feet are the distinguishing characters which can be most easily 

 observed. 



Four specimens were found in three gatherings. 



OiTHONA NANA Giesbi-echt. 



Occurred in five gatherings, but in tAvo only was it numerous. 

 Distribution,. N, Atlantic, Mediterranean, Red Sea, Arabian 

 Sea, Indian Ocean, Oulf of Califoinia, Cape of Good Hope. 



