ABT.5. NORTH AIVIERICAN PARASITIC COPEPODS WILSON. 69 



the axis of the antenna. There are no other spines except a terminal 

 tuft of 8 or 10 at the tip of the terminal joints, of which one is much 

 longer than the others and curves around backward toward the body ; 

 the rest are straight. 



The second antennae are stout and three- jointed; the basal joint is 

 considerably swollen and carries a small spine on its outer margin. 



The second joint is inserted in such a maimer as to stand out 

 diagonally from the ventral surface of the head. It bears on its 

 anterior surface at the center a large elliptical plate of corrugated 

 chitin, which is raised considerably above the surrounding sur- 

 face. The terminal joint is in the form of a strong claw, which is 

 strengthened at its base by two short and stout spines. 



The mouth tube is an elongated oval in outline, the tip rather 

 bluntly rounded. The opening is terminal or subterminal, and 

 through it can be seen the tips of the stylet-shaped mandibles. 



The first maxillae lie on either side of the mouth tube ; each con- 

 sists of a slender basal joint and two filiform rami, the enclopod 

 longer than the exopod and reaching beyond the tip of the mouth 

 tube. Both rami are armed with short hairs arranged like those of 

 plumose setae. The second maxillae are inserted far forward, close 

 to the edge of the carapace; in fact they stand opposite the base 

 of the mouth tube and are separated as far as possible from each 

 other. Each is three-jointed, the two basal joints being considerably 

 swollen and of about the same size, while the terminal joint is in the 

 form of a short, straight claw. This claw is dentate along its posterior 

 margin and also flanged with a circular flap near its tip. At the base 

 or the claw and extending back some little distance on the outer sur- 

 face of the second joint is a row of long stiff hairs. 



The maxillipeds are large, even for this genus, and their pattern 

 gives a ready means of identification of the species. They also are 

 set close to the edge of the carapace and as far apart as possible, but 

 are united across the midline by a broad band of chitin, which lies 

 just behind the mouth tube. The basal joint is stout and tapers 

 toward the distal end ; it extends diagonally outward and baclrward 

 beyond the margin of the carapace. At the base on the outer surface 

 there is a medium-sized knoblike protuberance, which is corrugated 

 and armed with short spines. The second joint is slightly narrower, 

 but still stout and considerably longer than the basal joint. It is, 

 however, strongly curved, so that the terminal joint is brought 

 directly over the knob just mentioned. This terminal joint is in the 

 form of a large chela, composed of a stout proximal and two distal 

 portions. Of the latter the inner one is the inarticulate branch of 

 the chela, and is a large knob with a corrugated inner surface. The 

 outer portion, the articulate branch, consists of three parts, two 



