72 CHARLES BRANCH WILSON 
Remarks. The host of this species attains a length of three feet and is 
said to be common all along the coast of South America from: Panama to 
Juan Fernandez, especially in the deep channels between the Galapagos 
Islands. 
Future examination of these fish ought to yield numerous specimens of 
this peculiar species. 
Caligus aesopus, new species. — Plate 3 fig. 8—10; 4 fig. 11—13. 
Host and record of specimens. Eleven mature females, most of them 
with egg strings, were taken from the mouth of a large scombrid (material 
lost; probably Serzola peruana), April 20, 1917 at Juan Fernandez (Masatierra). 
They are made the types of the new species. 
Specific characters of female. Carapace acorn-shaped, the same width 
and length, which latter is decidedly less than half the length of the entire 
body, rather squarely truncated posteriorly. Frontal! plates well defined, about 
half the width of the carapace; lunules large, circular, slightly projecting. Pos- 
terior sinuses closed and inclined slightly toward the midline; median lobe a 
little wider than the lateral ones and about the same length. Cephalic area 
three-fifths the width of the carapace, its sides angular at the center and pro- 
jecting strongly. Free thorax (fourth segment) spindle-shaped, the same width 
as the median lobe of the carapace; genital segment one-third longer than wide, 
with broadly rounded posterior corners, and a concave posterior margin; fifth 
legs visible at the posterior corners; a pair of short laminate processes project- 
ing from the center of the posterior margin on the ventral surface. Abdomen 
one jointed, one-third the length of the genital segment and nearly as wide 
as long; anal laminae small, widely separated, divergent, each with four short 
setae. Egg strings half the length of the body and rather narrow. 
First antennae with a long and slender terminal joint; second pair with 
a powerful terminal claw, which is curved like a sickle. Furca broadly Y-shaped, 
the base as long as the branches and nearly circular, the branches stout, blunt, 
and only slightly curved. 
Basal joint of first legs with a rudimentary endopod in the form of a 
one-jointed finger process; third legs with a large claw-like spine on the basal 
joint of the exopod. Fourth legs short, the basal joint as long as the three 
terminal joints and quite stout. At the base of the spine on the third joint, 
and of the outer spine on the terminal joint, is a thin circular lamina whose 
margin is cut into long acuminate teeth. 
Total length 5,4; mm. Length of carapace 2,3; mm. Length of genital 
segment and abdomen 2,5. mm. Width of carapace 2,35 mm. Length of egg 
strings 2,80 mm. 
Color (preserved material) a uniform cartilage gray without pigment mark- 
ings of any sort. 
