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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 39. 



first maxillae are in the form of stout knobs, each bearing two nearly 

 straight setse with or without plumes, which point backward and out- 

 ward, and can be seen projecting from the ventral surface of the head 

 in a lateral view. The second maxillse are made up of a stout basal 

 joint and a short terminal joint, curved forward similar to the man- 

 dible and armed with a thick tuft of setae at its tip. 



The chief difference between different species lies in the shape and 

 armature of the terminal joints of the mandibles and maxillae; the 

 maxillipeds are lacking. 



Male (fig. 28). — Mouth-parts in the same position as those of the 

 female, and the first three pairs similar in all respects. The mandi- 

 bles are perhaps turned a little more sharply forward, and the first 



maxillae are a trifle smaller than 

 in the other sex. But the dis- 

 tinguishmg characteristic is the 

 presence of a pair of powerful 

 maxillipeds in normal position 

 behind the other mouth-parts. 

 These are three-jointed and 

 both the terminal joints are en- 

 tirely free from the head. The 

 basal joint is very short and 

 merely serves to attach the 

 appendages; the second joint 

 is oblong, not much swollen, 

 tapers gradually toward the 

 distal end, and is furnished 

 with powerful muscles, Avhich 

 operate the terminal joint. 

 The latter is in the form of a 

 stout claw, in the particular 

 species (chautauquaensis) fig- 

 ured fully twice the length of 

 the second joint, curved into 

 nearly a semicircle, with the concave side facing that of its fellow across 

 the midline, and slightly enlarged and bluntly rounded at the tip. 



In their natural position these large maxillipeds are turned for 

 ward and cover the other mouth-parts. The latter are also bunched 

 together, the tips of the mandibles being underneath the tips of the 

 second maxillae, and the first maxillae being partially or wholly cov- 

 ered by the basal joints of the same appendages. In the figure here 

 given the distal portions of the mouth-parts have been separated in 

 order to show as much as possible the exact shape of each. 

 Their bases, however, are in their proper position. 



Fig. 28. — Mouth-parts of male Eegasilus chautau- 

 quaensis. lb, Labium; md, mandible; mi', first 

 maxilla; 7m", second maxilla; mip, maxilliped. 



