This singular Neotropical form is even more isolated than the Flamingo and more difficult to place satisfactorily in a linear series. It seems, however, that it is best arranged near the Anatidæ, as first suggested by Mr. Parker[7], and that it may with least inconvenience be constituted an aberrant family of the Order Anseres. [7] _Cf._ Proc. Zool. Soc. 1863, p. 511. Besides the typical form _Palamedea_ (with one species found in Amazonia and the interior of Brazil) the present family contains only one other genus--_Chauna_--in which the head carries a feather-crest instead of the long horny wattle of _Palamedea_. One species of _Chauna_ is met with in Argentina, the only other known species (_C. derbiana_) being confined to Colombia and Venezuela. 334. CHAUNA CHAVARIA (Linn.). (CRESTED SCREAMER.) +Palamedea chavaria+, _Burm. La-Plata Reise_, ii. p. 506 (Paraná). +Chauna chavaria+, _Scl. et Salv. Nomencl._ p. 128; _iid. P. Z. S._ 1868, p. 145 (Buenos Ayres); _Durnford, Ibis_, 1878, p. 63 (Buenos Ayres); _Gibson, Ibis_, 1880, p. 165 (Buenos Ayres); _Barrows, Auk_, 1884, p. 272 (Entrerios). _Description._--Slaty grey, blacker on the back; chin, neck, and cheeks whitish; a naked ring round the neck; nape crested; belly whitish; feet red: whole length 32·0 inches, wing 19·0, tail 8·0. _Female_ similar. _Hab._ Southern Brazil, Paraguay, and La Plata. This majestic bird, called _Chajá_ in the vernacular, is common throughout the Plata district, in marshes and on the open level country abounding in water and succulent grasses, and ranges south to the neighbourhood of Bahia Blanca. It is most abundant on the pampas south of Buenos Ayres city, and on that vast expanse of perfectly level, green country the bird is seen at its best; it is there an important feature in the landscape; its vocal performances are doubly impressive on account of the profound silence of nature, and its singularity--the contrast between its aerial habit and ponderous structure--strikes one more forcibly where the view is so unobstructed and the atmosphere so pure.