404 



BULLETIN- 15 8, UNITED STATES NATION" AL MUSEUM 



leaving the middle of the body comparatively free. Eye deep ruby- 

 red. 



Female. — Carapace ovate, about half the entire length, frontal 

 margin convex; lunules large and projecting; fourth segment short 

 and about one-third the width of the carapace; genital segment 

 quadrangular, wider than long, without lobes or leg rudiments. 

 Abdomen 1-segmented, a third as wide and a half as long as the 

 genital segment; caudal rami short and wide. Fourth leg 3-seg- 

 mented, with five spines and no seta. Total length, 5-7 mm. 



Mode. — Carapace as wide as long ; lunules larger than in the female ; 

 fourth segment as wide as the genital segment and more than a third 

 as long; genital segment spindle-shaped, without leg rudiments. 

 Abdomen as long as genital segment, 2-segmented, the basal segment 

 a little more than half as long as the end segment. Total length, 

 ^5 mm. 



Remarks. — This is the most common species of the genus and 

 apparently infests any host that offers. It may be recognized by the 

 pigment spots on the female and by the relative length of the two 

 abdominal 



segments 



in the male. Both sexes, especially young 

 females and males, are often taken in surface 

 tows, and are fully as active as any of the free 

 swimmers. 



CALIGUS CHE LIFER Wilson 

 FiGXJRE 251 



Caligus chelifer Wilson, Proc. U. S. Nat. Mus., vol. 

 28, p. 582, pi. 11, 1905. 



Occurrence. — Found on the external surface 

 of the menhaden, the swordfish, and the cutlass 

 fish at Woods Hole. 



Distribution. — West coast of Africa in 

 plankton (Brian). 



Color. — Body a more or less transparent 

 yellow, very thickly spotted on both dorsal 

 and ventral surfaces with branching pigment 

 blotches and lines of light rusty brown; eye 

 deep ruby-red. 



Female. — Carapace ovate, about half the 

 entire length ; lunules large, circular, and some- 

 what projecting; fourth segment one-fourth the width of the cara- 

 pace; genital segment acorn-shaped, as wide as long, squarely 

 truncated in females bearing egg strings, evenly rounded in immature 

 females. Abdomen slender, 2-segmented, terminal segment twice the 

 length of the basal; caudal rami cylindrical, three times as long as 

 wide, inclined inward toward each other. Base of the furca longer 



Figure 251. — Caligus chel- 

 ifer: a. Female, dorsal ; 

 bj female, fourth leg 



