NO. 1504. AMERICAN PARASITIC COPEPODS— WILSON. 709 



Free thorax segment nearl}- as wide as the genital segment, two- 

 tifths as long- as wide. Dorsal plates rather small and nearh^ orbicu- 

 hir, separated In' a wide median space. 



Genital segment half the width of the carapace, oblong in shape, 

 with nearly parallel sides and well-rounded angles. Its entire margin 

 is smooth and without any trace of the marginal fringe of spines or 

 the posterior prolongations on either side of the abdomen which are 

 present in other species. 



Abdomen two-jointed, the joints about the same size; on either side 

 of the tirst joint a semicircular wing or thin fold of skin projects out- 

 ward laterally from the dorsal surface, the combined width of the 

 joint and the two wings being about half that of the genital segment. 

 The tirst abdomen segment has a convex anterior and a concave pos- 

 terior margin. Tiie terminal segment is slightl}' spindle-shaped, with 

 comparativeh' small and elliptical anal laminse. The plumose sets on 

 these lamina? are smaller than in other species. Tlie egg-strings are 

 wide and about once and a half the length of the body. 



Anterior antenna? two-jointed, with the teriilinal joint much smaller 

 than the basal and strongl}' club-shaped. 



The posterior antennae have a large basal joint with a stout and well- 

 curved terminal claw. 



First maxillipeds the same as in all the Caligina^; second pair large 

 and stout, the terminal claw^ strong, but not much curved. 



On the inner margin of this claw near its tip is a small, flattened 

 flange which extends about a third of the length of the claw. The 

 two pairs of maxilla? are similar to those of gracilis^ but the first pair 

 are even more rudimentary and can be found oidy with difficulty. 

 The ventral ridges between the bases of the maxillipeds, which take 

 the place of the furca, are similar to those in gracilis, but are con- 

 siderably larger with deeper corrugations. 



The basipod of the tirst pair of legs is rather small, the exopod 

 almost exactly like that of gi-acilis in size, shape, and armature, but 

 the endopod is tpute diflerent. Its proximal joint is long with a ver^- 

 wide flange on the inner margin; attached to this flange where it joins 

 the basipod is a small strawberry-shaped papilla. The terminal joint 

 of the endopod carries three seta? of equal size as in carcharise. 



The second legs resemble those of gracilis very closeh' in segmen- 

 tation and armature, Ijut the joints are relativel}^ smaller. 



The third legs present several differences; the exopod is narrow and 

 nearh' as long as the endopod; its segments are much longer than wide, 

 thus separating the large claws with which each segment is armed. 

 The endopod is short and stocky and shows its segmentation distinctly. 

 The fourth legs are similar to those of the other species of the genus. 



