No. 2194. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 123 



crly and an elevated ridge around the margin of the anterior trun- 

 cated end. Frontal processes arranged in a definite jiattern, con- 

 sisting of a semicircle on either side around the margin, two shorter 

 bunches inside of them curved like parentheses marks, and two 

 narrow straight masses through the center dorsoventrally. (See fig. 

 143.) There is a wide, open space without processes between the 

 semicircle and the parenthesis mark on either side, and a narrower 

 space between the jDarenthesis mark and the central mass, so that 

 the pattern stands out very distinctly. 



At the posterior end of the cephalothorax nearer the dorsal surface 

 there is a single long horn on either side, which tapers gradually to a 

 bluntly rounded point, extends directly backward alongside the neck, 

 nnd is curved considerably forward toward the ventral surface. 

 The cliitin skin over these horns is very thin, and in consequence the 

 horns are soft and pliable. The neck is not enlarged anteriorly, but 

 starts abruptly from the back of the head between the horns, is the 

 same diameter throughout, and is much longer than the trunk. The 

 latter is twice the diameter of the neck and is transversely ridged; 

 abdomen half the length of the genital segment; plumules about 24 

 in number along each side of the abdomen, quite long and dicho- 

 tomously branched; egg strings very slender and longer than the 

 entire body. 



First antennae four-jointed, each joint heavily armed wuth setae, 

 separated from the second pair by a considerable distance (fig. 145) ; 

 the third joint is the shortest and narrowest, while the fourth or 

 terminal joint is the longest and widest. Second antennae large 

 and stout; basal joints triangular, considerably smaller than the 

 terminal joints and widely separated across the midline; second or 

 terminal joints swollen, with a stout and strongly curved claw, 

 which shuts against a medium-sized peg on the inner margin of 

 the joint. Between the basal joints is a wide chitin plate, in the 

 center of which is a large and bluntly pointed rostrum with a pig- 

 ment spot in its base. The chitin ring surrounding the esophagus 

 is diamond-shaped, with the two obtuse angles lateral, and each of 

 them giving off a wide chitin band; the other two bands are on 

 either side of the anterior point. The arrangement of the chitin 

 ribs and soft membranes is exactly like that of the frontal processes, 

 the soft membranes under the open spaces, the ribs under the 

 processes. 



The swimming legs each have a large spot of pigment on the basal 

 joint and the different pairs are separated by distances correspond- 

 ing to the numbers 1, 5, 6. 



Color. — Head and buried portion of the neck brownish yellow; 

 trunk dark cinnamon brown with interrupted transverse bands of 

 yellow ; plumose appendages dark steel-gray. 



