No. 2194. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 117 



the unteiior margin, and running the whole length of the ventral 

 surface to the neck. Ventrally the anterior two-thirds of this furrow 

 is filled with the small horny frontal processes, those along the mar- 

 gin of the gruo've larger than those along the bottom. First two 

 thorax segments as wide as the head, fused and separated from the 

 third and fourth segments by a groove ; they give off a pair of long 

 and slender lateral borns and a much shorter dorsal horn. 



Third and fourth segments also fused, narrower than the two first 

 segments and tapered posteriorly; neck very long and threadlike, 

 only the extreme anterior portion being yellow and chitinous, while 

 the rest is softer and the same color as the trunk. The latter is com- 

 paratively short and not much enlarged, its surface being raised into 

 irregular transverse ridges, lighter in color than the intervening 

 grooves. Posteriorly its dorsal portion passes into the abdomen, 

 which is short, tapering, transversely ridged like the trunk, and 

 bluntly rounded at the tip. 



Each barb of the plumose appendages is single and branched on 

 only one side; the first one or two branches (barbules) are much 

 larger than the others and are themselves dichotomously divided; 

 the egg strings are comparatively short and slender. 



The first antennae are removed some distance behind the second 

 pair, are three-jointed, and well armed with setae. The second 

 antennae are two-jointed and tipped with a chela ; the basal joint is 

 triangular, the apex of the triangle being attached to the dorsal 

 surface of the head and the base being articulated with the terminal 

 joint; the claw of the chela is stout and strongly curved, the peg is 

 sliort and considerably inclined inward toward the opposite antenna. 



The mouth tube is reduced to a mere fringe around an opening on 

 the ventral surface of the head, in the bottom of the groove and near 

 the sinus in the anterior margin. No mouth parts can be seen, but 

 instead the groove around the mouth is filled with the corneous 

 frontal processes. 



Buried dee])ly in the tissues over the base of the esophagus is an 

 eye which still retains the two lateral lenses found in larval forms. 



The four pairs of swimming legs are all present, the three pos- 

 terior pairs placed at distances behind the anterior pair represented 

 by the numbers 5, 17, 28; the first two pairs are biramose, the last two 

 uniramose, all the rami two-jointed and bearing setae. 



The structui-e of the mouth framework is clearly shown in figure 

 123; the esophngus is surrounded by a chitin ring (cr) oblong iii 

 shape, somewhat angular and attached to the inside of the wall of 

 the head. From each of its four corners and from the center of 

 cither side a sliort and wide chitin band (ch) projects dorsally into 

 the cavity of the head. 



