THE CANADIAN ENTOMOLOGIST. 195 



The viaxillcc are complex ] the stout cardinal piece is chitinous, bear- 

 ing on its surface two sharp hooked teeth ; the superior part is divided 

 into two lobes, the outer one is soft and fleshy, rounded at the apex, 

 having its surface beset with long, stiff hairs ; the inner one is concave 

 above, and bears at its apex four stout teeth, which have rounded extremi- 

 ties and the inner face concave ; along the inner surface of the lobe there 

 are several strong pointed curved spines. The maxillary palpi are four- 

 jointed ; the basal joint is short and broad \ the remaining articles dimin- 

 ish regularly in diameter ; the second and third are about the same length, 

 equal to twice that of the first ; the third is rounded at the end, and more 

 than half the length of the fourth. There are apparently several minute 

 tubercles on the rounded surface of the extremity. The same appear on 

 the corresponding joint of the labial palpi (Figs. 5 and 10). 



The labium extends over the under surface of the jaws nearly to their 

 tips ; its texture is membranous ; its surface is densely clothed with hairs; 

 the somewhat quadrate mentum is situated between the stout maxillae. On 

 its outer sides there are two elevated corneous pieces \ they each have a 

 pointed, tooth-like upper extremity. A long hair arises from its outer sur- 

 face. A faint suture divides the anterior or palpi bearing part from the 

 mentum. This piece is as wide as the distance between the maxillae ; the 

 front edge is bisinuate ; the labial palpi are situated at the posterior outer 

 angle of this palpigerous piece. They are three-jointed ; the first and 

 second are stout, and the terminal one narrower and bent inwards. These 

 organs project a httle beyond the anterior edge of the labium (Fig. 11). 



The legs are rather long and muscular. The tarsus ends in one strong 

 claw ; there are many stiff hairs over the surface. Above the claw there 

 is one long, straight bristle ; just above it, on the inside, there is a little 

 tuft of bristles. 



The branchiae are situated on the posterior border of the ventral surface 

 of the second, third, fourth, fifth and sixth abdominal rings — five pairs in 

 all.  The stout branchial trunk, a short distance above its origin, bends 

 outwards, and bears along its lower surface eleven long filaments, the 

 middle ones are longest. These long white organs are seen waving to and 

 fro continually while the animal is alive. This motion appears to be due 

 to the up and down strokes of the last segment, which repeatedly strikes 

 the water as the tail of a cray fish does when swimming. A large tracheal 

 tube may be traced, on either side, from the posterior border of the 

 eleventh ring forward, over the insertion of the branchiae, connecting with 



