BY R. .t. TILLYAUb, 



93 



the candle, and both it and the candle itself have become 

 flattened. This is well seen in Plate i., fig. 7. The gill is opaque 

 throughout, deeply pigmented in brown or black. Consequently 

 the tracheal system is very difficult to follow: but it can be seen, 

 in specimens fresh fiom ecdysis, to be veiy similar to that of 

 Neosticta, except that there are always only hvo main tracheae in 

 eacli gill. The cuticle is covered with short, shaggy hairs, 

 especially upon the distal joint. The length of the median gill 

 is 45 mm., that of the laterals 5 mm.; the former is slightly 

 wider, and its tip more rounded than in the latter. These gills 

 are held well apart from one another, the angle between the two 

 laterals being from 20° to 30°, while the median gill projects 

 above them at an angle of from 30° to 40°. 



p. TheNodate Vertical Lamella. (Text-fig.24; Plate ii., figs. 12-1 4). 

 This form of gill occurs in the three allied Australian genera 

 Caliagrioii., Pseudayrioii, and Austroagrion (also in the Palse- 

 arctic genus Erythromma). It is the most beautiful type of 

 caudal gill known, prin- 

 cipally because of the 

 wonderful dendritic ar- 

 rangement of the ter- 

 minal tracheal branch- 

 lets from NYhich the 

 capillaries are given off". 

 These branchlets are 

 short, knobby, and 

 densely pigmented, giv- 

 ing the eflfect of the 

 short, bent branches of 

 a densely branching oak 

 tree. The pigment is 

 especially dense at their 

 ends, and gives them 

 the " knobby" appear- 

 ance already mentioned, 

 as may be seen in Text- 

 fig.24.' 



nsp. 



Text-lig.24. 

 Portion of gill of Ca/iayn'oii hi/llnghursii 

 (Martin), to show the node and nodal 

 line. n.sp. nodal spine. From a cleared 

 whole mount; ( x 28), 



