AKT. 5. NORTH AMERICAN PARASITIC COPEPODS WILSON. 49 



glass, the dorsal plate all one piece, entirely covering the third and 

 fourth legs and Avrapped around ventrally like the skirts of a mili- 

 tary cloak flaring outward. 



Genital segment about as long as wide, its lateral margins not very 

 convex; abdomen half the width of the genital segment, much nar- 

 rowed anteriorly, widened through the posterior margin. Anal 

 laminae flattened dorsoventrally, the basal half of uniform width, the 

 terminal half tapered to a blunt point tipped with two small spines. 

 Egg strings wide, but not very long, projecting half their length 

 behind the dorsal plate. 



First antennae entirely concealed in dorsal and lateral views, at- 

 tached just above the bases of the second pair and apparently four- 

 jointed, the jointing being indistinct. The last joint is heavily armed 

 with setae. Second antennae composed of a stout basal joint and a 

 curved terminal claw. They also are entirely covered by the sides 

 of the cephalothorax, and can be seen only when the side flaps are 

 pushed back. The mouth tube is short and conical. The first maxil- 

 lae have an almost spherical inner portion, armed posteriorly with 

 a single large spine. The outer portion is much longer, tapers to a 

 blunt point, and is armed with two unequal spines, the largest one 

 posterior. The second maxillae have a stout basal joint and a nearly 

 straight terminal claw, which is bluntly rounded at the tip, where it 

 is armed with a row of fine teeth along either margin for a short 

 distance. 



The maxillipeds are large and stout, the basal joint much swollen, 

 and the terminal claw sharply curved near the tip. 



First and second swimming legs similar to those of the male, third 

 pair folded in the usual manner and extended in front of the body 

 parallel with each other and at right angles to the body axis. Fourth 

 legs biramose, divided not quite to the base, the rami flattened dorso- 

 ventrally into broad, bluntly pointed laminae, of which the exopod 

 is a little the longer. In young females the tips of these fourth legs 

 project beyond the posterior margins of the dorsal plate, but in the 

 fully developed adult the legs are entirely concealed. 



Color (preserved material) a uniform yellowish brown. 



Total length, 3 mm. Cephalothorax 1 mm. long, 0.85 mm. wide. 

 Anterior portion of dorsal plate 0.80 mm. wide, posterior portion 

 1.50 mm. wide. 



Speci-fic characters of male. — General form short and thick set like 

 the female; cephalothoi\ax almost circular in dorsal outline, a trifle 

 wider than long, with both pairs of antennae projecting from its 

 anterior margin. Body as wide as the cephalothorax and about twice 

 as long, the anterior corners evenly rounded. Genital segment rela- 

 tively much longer than in the female, its sides fused with the bases 

 of the fourth legs. Abdomen narrow, trapezoidal and short, the 



