322 STEPHEN G. RICH 



EXPLANATION OF THE FIGURES 



Note. — I have omitted in the figures of the rectum viewed from the dorsal 

 aspect most or all of the tracheal branches coming from the ventral side of the 

 tracheal trunks. This has been done to gain clearness and has been merely an 

 avoidance of parts duplicating those figured- 



The following are the abbreviations used: 



ah, button or pad on cephalic side of //, longitudinal fold 



gill ///(, longitudinal muscle band 



ac, anal canal int, Malpighian tubules 



hf, buttress fold PD, postdorsal trachea 



ch, button or pad on caudal side of gill -pg, pigment 



cm, circular muscle PV, postventral trachea 



cs, epithelial cushion r, rectum 



CT, tracheal connection between dor- rh, ridge and bulb on gill 



sal and ventral trunks s, setules 



D, dorsal tracheal trunk sa, superior appendage 



/, fat tissue si, small intestine 



Jh, boundary of fat tissue tr, trachea 



ff, fleshy fold V, ventral tracheal trunk 



g, gill V, lobe of anal valve 



ia, inferior appendage vi, villus 



L, lateral tracheal trunk +, cephalic edge of gill or cephalic 



/, lump at tip of gill • end of rectum 



la, lateral appendage 



Dorsal view of rectum of Cordulegaster diastatops. 



Ventral view of same. 



Schematic cross-section of same (from Andrews MS.). 



Plan of arrangement of internal folds of same. 



Longitudinal and buttress folds of same. 



Detail of edge of fold of same. 



Musculature and gill bases of Hagenius brevistylis. 



Dorsal view of rectum of Aeschna constrict a. 



Longitudinal and buttress folds of same. 



Longitudinal and buttress folds of Basiaeschna janata. 



Longitudinal and buttress fold of Boveria vinosa. 



Double row of Anax Junius. 



Gill of same, showing tracheation. 



Gill of same, showing cushions, fat, and pigment. 



Contour plan of double row of same. 



