BY R. J. TILLY A RD. W/ 



inner edge of tlie gill, but only for a short distance from the 

 base. In the resting position, the gills are held much as in the 

 constricted and nodate forms. 



The two genera with subnodate gills may be separated as 

 follows : — 



'Gills short and broad, not much pointed; nodal spines large; no spines 



developed along the mid-ribs.... Ceriwjrion Selys; (PI. ii., fig. lo). 



(iills rather long and slender, moderately well pointed; nodal spines 



rather small: spines developed along the mid-ribs as far as the 



level of the node IscJinnm Charp. ; (PI. ii., fig. 16). 



The gills of the following species are known:— 



1. Cpviagrion trnhfisren.^ Sel^^s. Length of both median and 

 lateral gills 2-5 mm."^ Median gill wider and less pointed than 

 laterals. Base of gill rather narrow, stalk-like, distal half 

 broadened out. Node situated about half-way along gill. 

 Colour dull greyish, a touch of yellowish-brown near bases; no 

 pigment-bands. Branch tracheae very closely crowded together 

 (Plate ii., fig. 15). 



'1. hchnura JiPterostwla Burm. Length of gills when full- 

 grown, median 5*7 mm., laterals 6 mm.; median gill slightly 

 wider and less pointed than laterals, and a little bent. Gills 

 lanceolate, the base only slightly narrowed; the width of the gill 

 increasing up to about three-fourths of the total length, when 

 the width quickly narrows as the edges approach the pointed 

 tip. Node situated at about two-fifths of the gill-length. Colour 

 pale yellow, cream, or pale green; no pigment-bands, but some- 

 times slight patches of brownish pigment may be seen at inter- 

 vals along the rachis. Branch trachea? very regularly arranged, 

 not closely crowded together (Text-fig. 25; Plate ii., fig. 16). 



3. Ischnura aurora Br. Closely resembling those of /. hetero- 

 fificta in structure and shape, but much smaller when full-grown 

 (only -Imm.). Colour greyish-black. (The larva is black, while 

 that of /. heterosticta is green or yellow). 



* Both the larvae taken and preserved by me were at the end of the 

 penultimate instar; a third larva was bred out, but the gills of the exuviae 

 shrivelled up. 



