502 PROCEEDINGS OF TITE NATIONAL MUSEUM. vol. xxvin. 



MaJe. — Carapace proportionally very laryo, twice as lono- und three 

 times as wide as the rest of the body, sliuhtly narrowed anteriorly; 

 frontal plates small and narrow; free segment even smaller relatively 

 than in the female, which is very unusual; o-enital seoment semilunar 

 in shape, nearly twice the width of the abdomen, with very long and 

 acuminate lobes at the posterior corners. Two pairs of setiferous 

 papilla^ one at the tips of the lobes and the other on the inner mar- 

 gins near the base. 



A])domen the same length as the genital segment and slightly 

 swollen near the tip; appendages as in the female, with the usual 

 increase in the size of the second antennae and second maxillipeds; 

 fourth legs proportionalh' longer and more slender than in the female. 



Total length 4 mm.; length of carapace 2.68 mm. ; width of same 

 2.35 mm.; length of genital segment 0.8 mm; length of abdomen 

 (>.7'.> mm. 



Color not given. 



{hah'i^tie, generic name of host.) 



Several examples of this species were obtained from the gills and 

 tins of West Indian species of the genus B<illst<-s. 



A few indi\'iduals in the chalimus stage were also found still fastened 

 by a frontal tilament. 



CALIGUS ISONYX Steenstrup and Lutken. 



Plate XIV, tig. 171; Plate XV, tigs. 184-186. 



Caligus isonyx Steenstrup and Lutken, 1861, [). 358, pi. ni, tig. 5. — Bassett- 

 Smith, 1899, p. 450. 



Fiuiiah'. — C-arapace consideral)ly less than half the entire length, as 

 wide as long, nariowed anteriorly; frontal plates not prominent; lunules 

 very small; antenna" short; posterior sinuses comparatively deep, with 

 parallel sides; median lobe scarcel}" one-third the entire width, its 

 posterior margin just even with those of the latcn-al lobes; free seg- 

 ment narrow, but long and not swollen nmch at the center; genital 

 segment acorn-shaped, narrowed into a slender neck, where it joins 

 the free segment, the sides synmietrically rounded, the posterior mar- 

 gin squarely trimcated. There are two pairs of rudimentary leg 

 papilhe on this segment, one on the lateral margins considerably pos- 

 terior to the center of the segment, the other at the posterior corners. 

 Abdomen two-thirds the length of the genital segment, quite wide, 

 and enlarged a little toward the tip; anal laminte terminal, very small, 

 and carrying small setaj; egg strings unknown. Frontal plates emar- 

 ginate between the lunules; basal joint of first antennae short; terminal 

 joint nnich longer, but scarcely protruding beyond the margin of the 

 carapace. 



Second antennae long and slender, with an elongated and narrow 

 terminal claw, strongW curved. 



