1886.] PROCEEDINGS OF UNITED STATES NATIONAL :MUSEUM. 313 



Four divisions of the body back of the head are plainly distinguish- 

 able on the dorsal side. These are separated by three shallow but well- 

 defined transverse grooves, having a backward extension, as represented 

 on plate XI, fig. 1. The first is just back of the short neck; the sec- 

 ond originates at the hinder ends of the thoracic wings, and extends 

 some distance backward, forming three sides of a rectangular figure; 

 the third starts at the median indentations on the sides of the abdo- 

 men, and, though similar in its course to the preceding, is somewhat 

 straighter. The above arrangement of the grooves is well marked on 

 the specimen figured, which is more perfectly preserved than any of the 

 others. In other specimens, they have the same relative position and 

 shape, but from distortion in alcohol present numerous irregularities,, 

 and the intervening spaces are often inflated, appearing like large 

 rounded knobs, while the margins may be much thickened. 



The genital segment is small ; the tail very small, globular, with two 

 moderately long setose processes projecting from the ventral side, and 

 stopping some distance in advance of the posterior extremities of the 

 abdomen. 



In lateral view the body presents a grotesque ai)pearance, the dorsal 

 contour being rather strongly and regularly arched, the head and prom- 

 inent antennae resembling somewhat a crested helmet, and the thoracic 

 appendages held out rigidly in front. 



The anterior antennae are very large, prominent, flattened, irregularly 

 subtriangular in outline, their lateral extension being somewhat greater 

 than their longitudinal. Being soft and flexible, they exhibit consider- 

 able variation in their outline, but the inner margins are generally con- 

 vex and closely adjacent or slightly overlapping, the posterior and the 

 autero-lateral more or less concave, the former sometimes nearly straight. 

 At the sides they project far beyond the anterolateral corners of the 

 head, their total spread being about equal to the greatest width of the 

 head. The lateral portions are much narrowed, rounded at the ends, 

 and armed with a few small setae or patiillae; the anterior extension 

 varies in width, being sometimes broadly rounded, at others more acute. 

 The inner posterior corners are more or less extended. Each antenna 

 appears to consist of only a single joint; in one specimen examined, 

 however (plate XI, fig. 5), there were traces of a division near the mid- 

 dle ; but this would i>robably have disappeared under compression. 



The posterior antennae are small compared with the anterior ; they 

 consist of a rather small bavsal joint, and a stout, moderately curved 

 distal joint, but slightly tapering, though sharply pointed. The horny 

 framework to which they are attached is comparatively large and strong, 

 and continuous from side to side. 



Figures are given of the second and third pairs of mouth organs. In 

 the former the terminal joint is very slender, sharply pointed, the basal 

 large; in the latter the terminal joint is curved and also slender, but 



