602 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvin. 



Male. — Carapace proportionally very large, twice as long and three 

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

 frontal plates small and narrow; free segment even smaller relatively 

 than in the female, which is very unusual; genital segment 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. 



Abdomen 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 antennas and second maxillipeds; 

 fourth legs proportionally 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 

 0.79 mm. 



Color not given. 



(balistse, generic name of host.) 



Several examples of this species were obtained from the gills and 

 fins of West Indian species of the genus Batistes. 



A few individuals in the chalimus stage were also found still fastened 

 by a frontal filament. 



CALIGUS ISONYX Steenstrup and Llitken. 



Plate XIV, fig. 171; Plate XV, figs. 184-186. 



Caligus isonyx Steenstrup and Lutken, 1861, p. 358, pi. in, fig. 5. — Bassett- 

 Smith, 1899, p. 450. 



Female. — Carapace considerably less than half the entire length, as 

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

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

 parallel sides; median lobe scarcely one-third the entire width, its 

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

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

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

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

 gin squarely truncated. There are two pairs of rudimentary leg 

 papilla? 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 lamina? terminal, very small, 

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

 ginate between the lunules; basal joint of first antenna? short; terminal 

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

 carapace. 



Second antenna? long and slender, with an elongated and narrow 

 terminal claw, strongly curved, 



