About thirty different species of the fish-eating family Ardeidæ occur within the limits of the Neotropical Region. Of these, eight or nine are found in greater or less abundance in the provinces of the Argentine Republic. Five of these species are widely distributed in North and South America; the others are restricted to the southern portions of the New World. 315. ARDEA COCOI, Linn. (COCOI HERON.) +Ardea cocoi+, _Burm. La-Plata Reise_, ii. p. 508 (Paraná, Tucuman, Cordova); _Scl. et Salv. Nomencl._ p. 125; _Hudson, P. Z. S._ 1875, p. 625 (Buenos Ayres); _Durnford, Ibis_, 1877, p. 189 (Buenos Ayres), et 1878, p. 399 (Patagonia); _Gibson, Ibis_, 1880, p. 158 (Buenos Ayres); _White, P. Z. S._ 1883, p. 41 (Cordova); _Barrows, Auk_, 1884, p. 271 (Entrerios). _Description._--Above grey; head above, wings, and tail plumbeous black; beneath white, neck and sides of belly striped with black: whole length 36·0 inches, wing 18·0, tail 7·0. _Female_ similar. _Hab._ North and South America. In size, form, and colour the Cocoi closely resembles the Common Heron of Europe; in flight, language, and feeding-habits the two species are identical, albeit inhabiting regions so widely separated. In the southern part of South America it is not seen associating with its fellows, nor does it breed in heronries; but this may be owing to the circumstance that in the temperature countries it is very thinly distributed, and it is highly probable, I think, that in the hotter regions, where it is more abundant, its habits may not appear so unsocial. Though they are always seen fishing singly, they pair for life, and male and female are never found far apart, but haunt the same stream or marsh all the year round. Azara says that in Paraguay, where it is very scarce, it goes in pairs and breeds on trees. On the pampas it makes its solitary nest amongst the rushes, and lays three blue eggs. The following general remarks on the Heron apply chiefly to the _Ardea cocoi_, and to some extent also to other species of the Heron family. I have observed Herons a great deal, and think that there is much to be said in support of Buffon's opinion that they are wretched, indigent birds, condemned by the imperfection of their organs for a perpetual struggle with misery and want.