562 GEOLOGICAL SURVEY OF THE TERRITORIES. 



EXPLANATION OF PLATE XIX. 



Fig. 1. Apus lucasanus, first foot ; cl, gnathobase ; cl, tliat of the following appendage. 

 Fig. 2. Apu8 cequalia, second pair of feet. 

 Fig. 3. Apus newberryi, $ , second pair of feet. 

 Fig. 4. Apus longicaudatus, second pair of feet. 



Fig. 5, Apus lucasanus, $ ; second pair of feet ; differs from the female in having the 

 filaments on the gill. 



