isias. 63 



antenna (fig. 5) situated between the eighteenth and 

 nineteenth joints ; eighteenth joint formed by the 

 coalescence of the normal eighteenth and nineteenth, 

 nineteenth by the twentieth and twenty- first, twentieth 

 by the twenty-second, twenty- third, and twenty -fourth. 

 Mouth organs and swimming feet as in Centropages 

 typicus. Fifth pair of feet, in the female, two-branched 

 (fig. 10), haying the outer branch of three broad laminar 

 joints, the second of which is produced at the inner 

 margin into a strong ciliated spine ; the third joint is 

 as large as the other two together, is fringed internally 

 with swimming seta* and bears at the apex one large 

 and one small spine; inner branch 1 -jointed, rudimen- 

 tary, and bears two apical setae. Fifth foot of the 

 male (fig. 11) also two-branched, that of the right side 

 being the larger ; the outer branch in both cases 2- 

 jointed, the second joint large and forming, especially 

 in the right foot, a broadly expanded lamina, bearing 

 three or four small marginal spines, and on the right 

 side a large terminal ciliated spine ; inner branch 

 rudimentary; that of the right side provided with 

 swimming setae and 2-jointed. Terminal spines of the 

 swimming feet (fig. 12) elongated, narrow, and bayonet- 

 like, finely pectinated on the inner margin. Abdomen of 

 the female divided into four, of the male into five seg- 

 ments, third segment in the male produced in front into 

 a spiniform papilla. Caudal segments as long as the 

 united length of the last two abdominal segments ; 

 setae equal to half the length of the abdomen. Length 

 xyth of an inch (1*5 mm.). 



This fine and very distinct species appears to be 



