COPEPODS OF THE WOODS HOLE REGION 525 



one more or less angular. The four rounded corners of the ventral 

 surface are also raised a little into globular knobs. 



Between the inner ends of the anterior pair of knobs projects the 

 mouth tube, and on its sides are the first pair of mouth parts, while 

 the second pair are in the groove between the two anterior knobs and 

 the median row of three knobs. Each second antenna on the side of 

 the mouth tube is made up of a laminate basal portion and two rami. 

 The endopod is 1-segmented, with a small spine on its inner surface, 

 the exopod is 2-segmented, the basal segment wider and longer than 

 the distal, which carries three apical spines. Each of the second 

 pair of mouth parts has a swollen basal segment and a slender ter- 

 minal claw; the latter is greatly thickened at its base and armed 

 there with a minute accessory spine, then abruptly narrowed and 

 curved into a sickle shape. 



The neck is one-fifth of the width of the head and is at least 

 half the entire length of the body ; it may be comparatively smooth 

 throughout or it may be rather profusely wrinkled. Where it joins 

 the trunk it is always deeply wrinkled, for this is the portion in con- 

 tact with the skin of the host, the head of the parasite and the neck 

 anterior to this being buried in the tissues beneath the fish's skin. 



The trunk is club-shaped, widening gradually and then narrowing 

 to a rounded posterior end; the greatest width is about one-third 

 of the length, and about the same distance in front of the posterior 

 end. The divisions between segments in the trunk are indicated by 

 definite breaks in the longitudinal musculature, and by more or less 

 distinct marginal indentations. But only two actual transverse 

 grooves are visible, one across the neck some distance behind the 

 head, and the other near the anterior end of the trunk. That there 

 is really an abdomen fused with that part of the trunk which repre- 

 sents the genital segment is indicated by another break in the longi- 

 tudinal muscles. The surface of the trunk is smooth, and if the 

 muscles are relaxed when the parasite is killed there are no pits at 

 the ends of the dorsoventral muscles. But if the parasite dies with 

 its muscles contracted, the entire dorsal and ventral surfaces of the 

 trunk are covered with such pits. The posterior processes arise from 

 the dorsal surface of the abdomen and are about half as long as the 

 trunk, parallel and curved a little ventrally. The ovisacs are only 

 half the diameter of the posterior processes, but are longer than the 

 entire body, each containing about 1,000 eggs. Total length, 20-25 

 mm. Head, 2 mm. long ; 3.5 mm. wide. Neck, 12 mm. long. Trunk, 

 9 mm. long. Ovisacs, 23-27 mm. long. 



Male. — Head one-half longer than the trunk, its dorsal surface 

 strongly inflated and covered with a carapace, both the carapace 

 and the inflation ending abruptly opposite the bases of the second 

 71937—32 35 



