128 Wilson New Species of Parasitic Copepods. 



spines on its dorsal surface and lateral margins. On the outer margin also, 

 at about the center of the posterior lobe, is fastened a triangular projection, 

 nearly as long as the lobe itself and toothed on its inner margin. Abdomen 

 cylindrical and two-jointed ; basal joint wider than terminal and about 

 half as long; terminal joint with spherical swelling at its center, ornamented 

 dorsally and laterally with spines. 



This species differs from the two already described in the genus (G. 

 hygomianus, Stp. & Ltk. and G. huttoni, Thompson) chiefly in the size and 

 shape of the dorsal plates on the free segment, in the grooving on the dor 

 sal surface of the carapace, in the fringe of long hairs on the lateral margin 

 of the carapace, and in minor details of the appendages, especially the first 

 maxillae and furca. The first maxillae are three-parted, the outer prong 

 broad and spatulate, the two inner ones shorter and acute. The furca 

 has bifid branches, the outer ones extending nearly at right angles to the 

 base of the central sinus, the inner ones slightly divergent, with a broad 

 U-shaped sinus between them. Color a uniform yellowish gray, somewhat 

 darker where the surface is raised in ornamentation. 



Total length, 11 mm.; width, 4.6 mm. 



Outside surface of swordfish. 



(ornatus, ornamented.) 



Alebion gracile sp. nov. 



Type from Vineyard Sound, Massachusetts. No. 8122 U. S. National 

 Museum. 



Female. Carapace elliptical, projecting somewhat at the center. Posterior 

 sinuses broad, somewhat enlarged at the base and dividing the carapace 

 into nearly even thirds. Both median and lateral lobes squarely truncated. 

 Free segment nearly as wide as genital segment and carrying a pair of dor 

 sal plates whose outer margins are strongly convex. Genital segment a 

 little more than half as wide as the carapace, widest at the center and pro 

 longed posteriorly on either side into a stout conical spine which reaches 

 beyond the tips of the anal laminae. Abdomen two-jointed ; first joint 

 larger than second, and extending backward on either side of the latter in 

 a blunt conical projection similar to those on the genital segment. The 

 terminal segment is strongly constricted at its base and is only about half 

 the width of the basal segment. Anal papillae large, nearly as long as the 

 terminal segment, and curved in toward each other at the tip. 



Of the appendages, the first maxillae are reduced to mere semicircular 

 plates attached flatly to the ventral surface of the carapace, while the sec 

 ond pair are also flat laminae but considerably larger. The exopods of 

 the first three pairs of swimming legs carry the stout corneous claws pecu 

 liar to this genus, and the fourth pair are so rudimentary as to be invisible 

 in dorsal view. The fifth pair is entirely lacking. 



Male. The most noticeable difference between the male and female is 

 in the proportion of the different body regions. The carapace is orbicular 

 rather than elliptical while the rest of the body is strongly narrowed, mak 

 ing the contrast between the two very striking. The free segment lacks 

 the plates on its dorsal surface but carries on either side a rounded protub- 



