IN THE LAKV^ OF ANISOPTEEID DRAGONFLTES. 165 



Another striking peculiarity o£ this gill-basket is the enormous size of the 

 basal pads (text-fig. 11). These appear like rows of large brown buttons 

 along the sides o£ the lamellse, and are easily seen with the naked eye. 

 These organs certainly reach their greatest development in this tribe. Their 

 large size indicates probably, however, an earlier stage in the localization o£ 

 these organs as appurtenances of the separate lamellge. Originally, in the 

 Simplex System, they spread along the whole anterior border of the cross- 

 folds, besides supporting the main folds. When these latter deteriorated, 

 and the cross-folds began to develop as lamellae, localization of the basal pad 

 began in the shape of a condensation to a rounded pad in a fixed position, 

 with corresponding deepening of pigmentation. Hence the enormous pads 

 of the Syntliemini may be rightly regarded as an intermediate stage between 

 the non-localized pads of the Simplex System and the extremely reduced 

 separate localized pads of the higher Lamellate Types. 



The shape of the lamellae in the Synthemini is fairly typical of the sub- 

 family Corduliince as a whole, as well as of the lower Libellulince. Each 

 lamella is distinctly " hump-backed " or " nodding," the inner edge being 

 much more convex than the outer, so that the lamellae " nod ^' away from 

 the axis of the holobranch, slantwise towards the posterior end of the rectum. 

 Owing to the narrowness of the giJl-basket, the lamella of the Synthemini 

 are not so elongated as those of other genera. This is particularly noticeable 

 in Metathemis guttata, where the breadth of the lamella near its base is 

 nearly as great as the length from base to tip (Plate 20. fig. 9). A distinct 

 tracheal vertex is always present. The capillaries, though very numerous 

 fall behind those of other genera in fineness. 



(2) Austrocordulia. — The lamellae of the gill-basket in the larva of this 

 genus, the only one known for the tribe Idocorduliini, is the most remark- 

 able in the whole range of the Lamellate Type. There are a very lar^e 

 number of lamellae (2Q to 30) in each hemibranch, and they are closely 

 packed together. The tubercles separating the lamellae are large, and easily 

 seen under a low power. The basal pads are fairly large, showing a very 

 dark brown circumference with a pale orange-brown centre. The lamellae 

 themselves are of typical Corduline form, strongly nodding, considerably 

 longer than wide, and carry a very large number of capillaries of moderate 

 fineness. But the most extraordinary thing about them is that each lamella 

 is furnished, at its nodding tip, with a short and icell-developed papilla. This 

 papilla I propose to call the supravortical papilla, since it lies directly over 

 the lamellar vortex (text-fig. 15). The papilla is a simple eversion of the 

 wall of the lamella at its tip, into which a very few capillary loops have 

 been drawn or sucked. Its structure is essentially similar to that of the 

 papillae in Anax, from which it differs only in being much shorter and wider. 

 Its cuticle is armed with nine or ten strongly-hooked chitinous teeth all 

 bent towards the outer edge of the lamella. Text-fig. 15 shows this papilla 

 highly magnified. 



LINN. JOURN. ZOOLOGY, VOL. XXXIII. 12 



