With no one group of the Australian birds have I had so much difficulty in discriminating the species as the genus _Podargus_. It is almost impossible to determine with certainty the older species described by Latham; could this have been done satisfactorily, even in a single instance, it would have greatly facilitated the investigation of the remainder. Messrs. Vigors and Horsfield regarded the specimens in the Linnean Collection as referable to three species, and have described them under the names of _Stanleyanus_, _humeralis_, and _Cuvieri_; Latham’s description of the species named by him _megacephalus_ accords so well with the _P. Stanleyanus_, that I suspect both those terms have been applied to one and the same species, an opinion strengthened by Latham’s remarks as to the great size of the head and mandibles of his bird, the total length of which he states to be thirty inches, which is evidently an error. After examining a large number of specimens comprising individuals of all ages, I have come to the conclusion that the Australian members of this genus constitute six species; four of which, namely, _P. megacephalus_, _P. humeralis_, _P. Cuvieri_, and _P. brachypterus_, are most closely allied to each other; and two, namely, _P. plumiferus_ and _P. Phalænoides_, which present specific characters that cannot be mistaken. We have then in Australia a large group of nocturnal birds of this form destined, as it would seem, to keep in check the great families of _Cicadæ_ and _Phasmidæ_, upon which they mainly subsist; but they do not refuse other insects, and even berries have been found in their stomachs. They are an inanimate and sluggish group of birds, and do not procure their food on the wing so much as other _Caprimulgi_, but obtain it by traversing the branches of the various trees upon which their favourite insects reside; at intervals during the night they sit about in open places, on rails, stumps of trees, on the roofs of houses and on the tombstones in the churchyards, and by superstitious persons are regarded as omens of death, their hoarse disagreeable voice adding not a little to the terrors induced by their presence. In their nidification the _Podargi_ differ in a most remarkable manner from all the other _Caprimulgidæ_, inasmuch as while the eggs of the _Ægothelæ_ are deposited in the holes of trees, and those of the members of the other genera of this family on the ground, these birds construct a flat nest of small sticks on the horizontal branches of trees for the reception of theirs, which are moreover of the purest white.