BY R. J. TILLYAUD. 79 



The structure of the distal joint, examined in sections, is seen 

 to be rather peculiar. It is, in fact, intermediate between the 

 true saccoid type and the triquetro-quadrate type, being slightly 

 flattened laterally, as seen in Text-fig. 16. The alveolar mesh- 

 work is present, and is supported by numerous horizontally-placed 

 internal laminae (il). The tracheae in this joint are all of small 

 size, the main stems quickly breaking up into numerous small 

 branches. The two blood-canals unite soon after entering the 

 basal part of the joint. 



The length of the gills in Neosticta is 5-6 mm., of which the 

 distal joint occupies at the most one-third. Their greatest 

 breadth is about l'2mm. The gills of Nososticta closely resemble 

 those of Neosticta in size and shape, but may be distinguished, 

 in common with the whole larva, by being of a more definite 

 black-and-white banded pattern, the pattern in Neosticta being 

 banded dark brown and pale yellowish-brown. 



B. The Tpiquetro-Quadrate Type. 



(Text-figs. 17-1 8; Plate iii., figs.23-24; Plate v., figs.34-35.) 



This type is not represented in Australia, being confined to 

 the Calopterygince, which are absent from our continent {though 

 the genus Neurohasis occurs in Papua). Through the kindness 

 of Dr. P. P. Calvert, of Philadelphia, I have been able to section 

 and study a number of gills of this type taken from larvae of un- 

 determined species of Calopteryx and Hetcerina. The import- 

 ance of this type of gill is that it forms a connecting-link or 

 intermediate stage between the Saccoid and Lamellar Types. I 

 shall not, therefore, attempt to elucidate specific or even generic 

 differences, which are of no importance for the purposes of this 

 paper. An ideal transverse section of this type of gill, taken at 

 about one-third of the total length of the gill from the base, is 

 shown in Text-fig. 17. 



The term triquetro-quadrate, which I have suggested as suit- 

 able to denote the type of gill-s\^stem found in the Calopterygino'^ 

 is intended to suggest the form of the transverse section across 

 the three gills. The lateral gills, which are always considerably 

 longer than the median, might be best described as triangular 



