No. 2104 NORTH AMERICAN PARASITIC C0PEP0D8— WILSON. 99 



spinelike horns just in front of tlie flexure. Beyond the flexure it 

 enhirges gradually until it joins the trunk on the ventral surface and 

 at the median line. 



There is a large spherical swelling on either side of the genital 

 segment at the anterior end, which starts on the dorsal surface and 

 reaches almost to the ventral surface. It may even be said that it 

 does reach that surface since its contour is indicated by a slight 

 notch on the ventral margin. There are two small knobs on the ven- 

 tral surface just in front of the egg coils, and a pair of lateral fleshy 

 flaps or processes over the bases of the egg strings, which are elon- 

 gated dorso-ventrally. 



The genital segment passes insensibly into the abdomen, which is 

 short, nearly straight, and twisted on its axis, so that the anal sinus 

 shows in a side view of the trunk. Over the base of the abdomen 

 two large processes are fused across the dorsal midline like a large 

 saddle. 



The Qgg coils are a little longer than the abdomen and taper to- 

 ward their tips. The first antennae are three-jointed and well armed 

 with setae; the second antennae are stout and two-jointed, the ter- 

 minal joint a little narrower than the basal and armed at the tip on 

 the outer margin with a stout curved claw, which shuts down inside a 

 raised semicircle on the opposite inner margin. 



Proboscis well developed and projecting from the ventral surface 

 of the head; upper lip split lengthwise through the center, each half 

 considerably wider than the mouth tube; the latter divided and 

 grooved on the ventral surface and a little flattened on the dorsal 

 surface; maxillae three-jointed, with a short and bluntly-pointed 

 terminal claw. 



Four pairs of swimming legs, the first and second pairs close to- 

 gether and a short distance behind the mouth, each biramose, the 

 rami one-jointed, the endopod considerably smaller than the exopod, 

 both well armed with plumose setae. The third and fourth pairs are 

 on the posterior margins of their respective thorax segments; each 

 is unirainose, the ramus one-jointed and armed, the third pair with 

 five, and the fourth pair with four, large plumose setae. The rela- 

 tive distances of the three posterior pairs behind the first pair are 

 represented by the numbers 1, G, and 11. 



Color (preserved material), a uniform orange yellow, the egg 

 strings brown, the head and anterior thorax white. 



Total length, if straightened, 20 mm.; from the flexure in the neck 

 to the tip of the abdomen, 11 mm. Diameter of head through lateral 

 processes, 1.25 mm. Diameter of genital segment, 4 mm. Diameter 

 of abdomen behind the saddle, 2 mm. Length of egg coils, 6 mm.; 

 diamctor, 1.50 mm. 



{diceraus, 8is, two and /cepas, horn.) 



