438 BULLETIN 15 8, UNITED STATES NATIONAL, MUSEUM 



sinus. Genital segment elliptical, its posterior lobes broad and 

 evenly rounded ; sixth segment plate as wide as long, narrowed ante- 

 riorly; caudal rami much shorter than the sixth segment plate, 

 widely divergent, and acutely pointed. Total length, 7-8 mm. 



Male. — Carapace wider than long, its posterior lobes broadly tri- 

 angular and slightly curved, accessory lobes very short, twice as 

 wide as long. Second, third, and fourth segments about the same 

 length, but diminishing rapidly in width, the fourth segment one- 

 fourth narrower than the genital segment, with strongly convex 

 lateral margins. Genital segment elliptical, one-third longer than 

 wide; rudiments of fifth and sixth legs the same size and bluntly 

 rounded, the sixth pair unarmed. Abdomen longer than wide, 2-seg- 

 mented; caudal rami foliaceous, each with three apical setae, and 

 one on the inner margin removed from the others. Total length, 

 7-7.5 mm. 



Remarks. — This is by far the most common specie,s of the genus in 

 the area, and the sand shark is its usual host. The female can be 

 identified by the large circular sinus between the plates of the third 

 segment, and the male by the size and shape of the rudiments of the 

 fifth and sixth legs. 



Genus NESIPPUS Heller, 1865 



Female. — Head fused with first segment, carapace transversely 

 elliptical, much wider than long; second and third segments fused, 

 with a single pair of dorsal plates, fourth segment free, with a pair 

 of small plates. Genital segment elliptical, considerably enlarged, 

 much longer than wide, with an evenly rounded outline and no pos- 

 terior lobes or leg rudiments. Abdomen 1-segmented, attached to 

 the ventral surface of the genital segment and invisible in dorsal 

 view; caudal rami large and foliaceous. Fir,st four pairs of legs 

 biramose, rami of first three pairs 2-segmented, of fourth pair 1-seg- 

 mented; Q^gg strings much longer than the entire body. 



Male. — Carapace longer than wide, with posterior but without ac- 

 cessory lobes; second, third, and fourth segments all distinct, about 

 the same length but diminishing in width, the fourth segment wider 

 than the genital segment, all three segments without dorsal plates. 

 Genital segment more or less angular, without lobes or leg rudiments ; 

 abdomen small, 1- or 2-segmented, wider than long; caudal rami 

 small but armed with long plumose setae. One species within the 

 present area. 



NESIPPUS ALATUS Wilson 



FiGUEE 276 



Nesippus alatus Wilson, Proc. U. S. Nat. Mus., vol. 33, p. 426, pis. 34, 35, 1907. 



Occurrence. — Found in the throat of the common sand shark, the 

 thresher shark, the great white shark, the dusky shark, the smooth 



