NO. 1788. NORTH AMERICAN ERGASILID^— WILSON. 331 



taken at Woods Hole, Massachusetts. These have even more para- 

 sites on them than the foregoing, one of the gills being almost literally 

 covered. A seventh lot was collected by S. G. Worth at Franklin, Vir- 

 ginia, from the same host, and is numbered 13019. 



These records prove that this species is common on the striped bass 

 along the entire Atlantic coast, and the examination of such fish in 

 any of the markets where they are kept for sale will almost certainly 

 yield specimens of the parasites. 



ERGASILUS CENTRARCHIDARUM Wright. 



Plate 42, text-figures 2, 3, 7, 13 to 25, 27, 29 to 38. 

 Ergasilus centrarchidarum, Wright, 1882, p. 243, pi. 1, figs. 12-18. 



Female. — Cephalothorax elliptical, projecting a little at the center 

 of the frontal margin and nearly as broad as long, the proportion being 

 about 85 to 110 in young females and 90 to 100 in mature adults. In 

 the latter this region is so strongly inflated by the genital products 

 that it also projects backward over the free segments and hides them 

 in dorsal view. Lateral constriction between the head and first tho- 

 rax segment barely noticeable in the young, not visible at all in the 

 adult. First three free segments about the same length and regu- 

 larly narrowed backwards, the first of them (second segment) less than 

 half the width of the cephalothorax. Fifth segment very short and 

 narrow; genital segment no wider and barrel-shaped, with rounded 

 sides. Egg-sacks cylindrical or cigar-shaped and a little longer than 

 the entire body; eggs of good size and arranged in five or six longi- 

 tudinal rows, about 100 in each sack. Abdomen half the width of the 

 genital segment, three-jointed, the middle joint a little shorter than 

 the other two. Anal laminae large, as long as the terminal joint of 

 the abdomen and each armed with three setae, of which the inner one 

 is from two to three tinjes as long as the two outer ones, which are of 

 about the same length. 



First antenna six-jointed, the joints unequal in length and not cor- 

 responding in different individuals, nor even in the two antennae of 

 the same individual. Usually the second joint is the longest and the 

 sixth is next. 



These antennae originate on the under surface of the frontal pro- 

 jection and some distance apart; each joint bears one or more simple 

 setae, the longest of which are as long as the entire antenna. The 

 setae on the first four joints are directed chiefly downward; on the last 

 two joints backward and outward. To judge from the innervation 

 of these antennae they must constitute very delicate tactile organs. 

 Second antennae a little longer than the cephalothorax, but always 

 carried folded up so that they reach only to the mouth, or slightly 

 beyond. Antennary sternum between the bases of these appendages 



