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 nurnerous 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 Seriola peruana), April 20, 191 7 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. 



F'irst 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 5,45 mm. Length of carapace 2,35 mm. Length of genital 

 segment and abdomen 2,50 mm. Width of carapace 2,35 mm. Length of eg'g 

 strings 2,80 mm. 



Color (preserved material) a uniform cartilage gray without pigment mark- 

 ings of any sort. 



