No. 2194. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 125 



never equaling them. None of the lateral horns were as long as in 

 Wright's figure, and they were usually slender, the stoutest ones 

 measuring 2 mm. in diameter. They sometimes taper and sometimes 

 enlarge toward the tip, are of about the same size and length on the 

 two sides, and usually project at an angle of 45°. 



The head varies in the proportion of length to breadth, but is 

 always wider than long, rarely twice as wide as long; it is generally 

 divided into two lobes, though sometimes obscurely, by a groove 

 which runs the length of the ventral surface, makes a slight depres- 

 sion on the frontal margin, and disappears on the dorsal surface." 

 The anterior end of the head is more or less flattened, rarely slightly 

 concave, and is inclined toward the ventral surface. This flattened 

 portion is covered with frontal processes branched like cauliflowers, 

 which are packed closely together, are quite uniform in size, and 

 present an even contour. 



The proboscis is elongated doi*so-ventrally and is completely hidden 

 by the frontal processes, which form a double ring or band about 

 it, the separation between the two rings being only slightly but 

 usually distinctly indicated. Along the anterior margin of the head 

 are a number of small protuberances similar to, but larger than, the 

 frontal processes, with which they are usually continuous. There is 

 one on each side of the longitudinal groove, those on the ventral side 

 being nearer together, those on the dorsal side farther apart. On 

 the sides of the head there may be anywhere from one to eight of 

 these processes, not regularly placed, and often more or less digitate 

 like cauliflowers. 



The antennae are situated somewhat in front of the center of the 

 dorsal surface, about one-third of the distance from the anterior 

 margin. The integument covering the head is very thin and yielding 

 to the touch ; the horns and the anterior thorax are much more rigid. 



The thorax varies considerably in length; anteriorly it joins the 

 head abruptly, retains a uniform width for most of its length, and 

 enlarges gradually at the posterior end to meet the trunk. The latter 

 is ribbed transversely, the ribs being sometimes quite prominent, at 

 others but faintly indicated. It is of uniform diameter (twice that 

 of the neck) as far back as the vulvae, where it is abruptly con- 

 stricted to two-thirds its former diameter, and from thence tapers 

 gradually to a bluntly rounded tip. 



The filamentous appendages are very numerous and dense, and are 

 directed backward and ventrally, leaving the dorsal side of the 

 abdomen clear; they extend slightly beyond the anus. 



The swimming legs are just behind the head, where they occupy 

 one and a quarter to one and a half millimeters of linear space. The 

 two anterior pairs are close together and overlap more or less, while 



