THE ERODII. 129 



towards the furcula, which, in the true Herons, especially A. russata WAGL., is much longer, and in 

 Cancroma (Plate VIII, fig. 13) even meets in the middle with its fellow of the opposite side. These 

 are the most important and peculiar characters of the pterylosis in Ardea ; I therefore merely men- 

 tion that all the Herons possess short but strong femoral tracts, which come in contact posteriorly 

 with the powder-down-tracts, and that the upper surface of their wings presents a continuous 

 plumage separated by a narrow space from the axillary tract which contains very strong feathers. 

 Beneath the greater part of the wing is a space in which, on the humerus, stand the strong 

 feathers of the hypopterum. These pass on to the breast and meet the inferior tract (Plate VIII, 

 figs. 10 and 12). The parapterum (fig. 11) is not less strong. On the margin of the wing I 

 counted from twenty-five to twenty-nine remiges according to the size of the species; of these ten 

 stand on the pinion. The third is usually the longest, although but little longer than the preceding 

 and following ones ; the others from the fifth onwards become more rapidly abbreviated ; the first 

 two or three usually possess an angular emargination at the apex of the inner half of the vane. 

 The tail generally contains twelve feathers, but in several species (e.g., A. stellaris, in which, however, 

 eleven or twelve are sometimes present, scapularis and tigrina) only ten, or even nine (A. sibilatrix). 

 According to the number of powder-down-tracts, the position of which has already been 

 described, two groups of Herons may be distinguished, and these also present other differences : 



A. Four such tracts, or two pairs, occur in A. minuta and stellaris. 



B. Six powder-down-tracts are possessed by A. scapularis, ralloides, tigrina, virescens, 

 nycticorax, sibilatrix, russata, WAGL., leuce, egretta, speciosa, WAGL. (malaccensis, ALIOR.), 

 cinerea, and purpurea. 



2. Cancroma (Plate. VIII, figs. 13 and 14). The pterylosis agrees in its general arrangement 

 with the type of the true Herons, and only differs in the circumstance that the lateral neck-tracts 

 are somewhat broader, and the inner branch issuing from its lower extremity runs down the 

 furcula until it meets the opposite one at an acute angle. Another distinction is to be found in the 

 form of the pectoral part of the inferior tract, which possesses a very distinct free outer branch, four 

 feathers in breadth, with which a slightly everted tip of the hypopterum is united. The main stem 

 itself is biserial, and much weaker than the branch ; it passes along nearer to the crest of the sternum 

 than in the true Herons, and turns more inwards upon the belly, so as to leave more room for 

 the somewhat larger inguinal powder-down-tracts. The dorsal tract is as in the Herons, but the 

 hinder part has its simple uropygial band somewhat longer. By these means also more room is 

 left for the powder-down-tracts situated beside it, and this they entirely fill. The lumbar tracts 

 are proportionately shorter and weaker. In the wing I counted twenty-two remiges, and ten on 

 the pinion ; the first are somewhat falciform, and attenuated at the end of the inner vane ; the 

 third, fourth, and fifth are the longest. In the tail I found only ten feathers ; and I also missed 

 the down-feathers among the contour-feathers. 



3. Eurypyga (Plate VIII, fig. 15). The uninterrupted plumage not only of the head, but 

 also of the entire neck, is indisputably the chief distinction of this genus from Ardea. From the 

 extremity of this ptilosis continua the dorsal tract starts in the form of two parallel biserial 

 bands, which extend as far as in Ardea. From each band there springs a row of weak feathers, 

 which very soon unite to form the weak, biserial, uropygial band. This commences as far up as 

 the middle of the back, and only terminates at the oil-gland, near which the remarkably long 

 but narrow lumbar tracts unite with it. Exactly in the space thus formed by each lumbar tract 

 and the uropygial band there is a powder-down-tract, which fills it completely, at least behind. 



17 



