402 



BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



Figure 248. — Caligus schistonyx: a. 

 Female, dorsal ; b, female, fourth 

 leg 



legs bipartite; fourth leg 3-segmented, with six spines and no seta, 

 the inner terminal spine much the longest. Total length, 3.8-4.2 mm. 



Male. — Carapace trapezoidal, as 

 wide as long, widest near the pos- 

 terior margin ; fourth segment as wide 

 as the genital segment and longer 

 than in the female; genital segment 

 one-fourth the width of the cara- 

 j)ace, with leg rudiments on its lateral 

 margins behind the center. Abdo- 

 men 2-segmented, end segment three 

 times as long as basal segment, the 

 two combined longer than the geni- 

 tal segment; caudal rami as wide as 

 long, their inner margins ciliated. 

 Total length, 2.8-3.2 mm. 



Remarks. — Both sexes, especially 

 the males, are sometimes captured 

 while swimming freely in the plankton. The species can be identified 

 most easily by the divided terminal claws on the first legs. 



CALIGUS RUFIMACULATUS Wilson 



FiGUBE 249 



Caligus rufimaculatus Wilson, Proc. U. S. Nat. Mus., vol. 28, p. 561, pi. 5, 1905. 



OccuiTence. — Both sexes found on the outside surface of the two 

 species of Fundulus so common around Woods Hole, and on the mul- 

 let ; also captured in the surface tow off the wharf of the Bureau of 

 Fisheries. 



Distribution. — Not found outside of the present area. 



Color. — Body pale straw yellow, covered on both dorsal and ven- 

 tral surfaces with irregularly scattered spots and lines of reddish- 

 brown pigment, more numerous on the genital segment; eye a deep 

 red. 



Female. — Carapace more than half the entire length ; frontal mar- 

 gin squarely truncated; lunules large and widely separated; genital 

 segment as wide as long, widest near the posterior margin, its pos- 

 terior corners without lobes or leg rudiments. Abdomen 1-seg- 

 mented, three-fourths as long as genital segment; caudal rami short 

 and stout, with convex inner margins. Furca the shape of an hour- 

 glass, with flattened branches; fourth legs 3-segmented, with five 

 spines and one seta, the inner terminal spine the longest. Total 

 length, 3.5-3.7 mm. 



Male. — Carapace relatively much larger than in the female ; fourth 

 segment nearly as wide as the genital segment and a third as long; 



