NO. 1788. -NORTH AMERICAN ERGASILID^— WILSON. 343 



ERGASILUS CHAUTAUQUAENSIS Fellows. 



Plate 46, text figures 26 and 28. 



Ergasilus chautauquaensis, Fellows, 1887, p. 175, preliminary notice; 1888, p. 

 246, 8 figs. 



Female. — Body with an elongate cyclops form, about four times 

 as long as wide ; head fused with the first thorax segment, the union 

 being indicated by a notch in each lateral margin and a partial groove 

 across the body. This cephalothorax considerably less than half the 

 entire length; contracted anteriorly to a narrow rostrum less than 

 one-quarter the width of the body; somewhat narrowed and squarely 

 truncated posteriorly. First three free thorax segments diminishing 

 regularly in width, the third one (fourth segment) being the same 

 width as the genital segment. The fifth segment is practically 

 indistinguishable between the fourth and genital segments; the latter 

 is barrel-shaped and narrowed considerably posteriorly. Abdomen 

 made up of three joints of the same length and width; on the ventral 

 surface the groove between the genital segment and the abdomen, 

 and each of the abdomen grooves is set with a row of long spine-like 

 teeth (see fig. 87). Anal laminae as long as the entire abdomen; 

 each nearly half as wide and tipped with two setse of about the same 

 size and four times as long as the laminae. 



Egg-sacks oval, onl}^ reaching to the tips of the anal laminse; eggs 

 quite large and arranged in four or five longitudinal rows, about 25 

 in each sack. 



First antennae six-jointed and longer than the second pair, the 

 setae on the fourth, fifth, and sixth joints very long, reaching to the last 

 thoracic segment. Second pair rather weak for this genus; four- 

 jointed, the basal joint not swollen as in most species. Labrum so 

 thoroughly fused with the head as to be indistinguishable. Mandi- 

 bles with a short and very wide basal joint, the neck short and narrow, 

 the cutting blade long and narrow and densely fringed with bristles 

 along both margins ; palp narrow and with a row of fine teeth along 

 its outer margin. First maxillos narrow, each furnished with two non- 

 plumose setae of about the same size. Second maxillae with a long and 

 narrow basal joint; the terminal joint also rather long and with a 

 dense tuft of bristles at the tip. Both mandibles and maxillae are so 

 placed that they overlap considerably across the mid-line. Labium 

 well curved but so narrow as to be little more than a chitin rib. 



First four pairs of swimming legs biramose; rami three-jointed, 

 except the exopods of the fourth legs, which have only two joints. 

 Fifth legs reduced to a long spine on either side of the fifth segment. 

 The following is the arrangement of the spines and setae on the first 

 four legs: First exopod, I-O; 0-1; II-5: endopod, 0-1; 0-1; 11-4: 



