It may be added that between Azara and his friend Noseda there was a great controversy respecting the parasitical habits of the common Cow-bird (_Molothrus_), which were first discovered by the former; and disbelieved in by Noseda, who accounted for the fact that the Cow-bird is never seen to make a nest by supposing that species to be the year-old young of the Chopi, which, he further imagined, took three years to acquire the adult form and plumage. Such an idea might seem to discredit Noseda as a naturalist, if we did not remember that Gilbert White at the same period was trying to prove the hybernation of Swallows in England. The whole of the discussion appears in the 'Apuntamientos,' under the description of the Chopi; and Noseda is there allowed to state his own case; after which the better observer, Azara, gives five objections to the theory, any one of which would be sufficient to demolish it. Fam. XII. CORVIDÆ, or CROWS. The typical black Crows and Ravens do not penetrate into the New World so far south as South America, their range terminating in the highlands of Guatemala and the islands of the Greater Antilles. They have, however, as representatives in South America several allied groups, clad mostly in various shades of blue, and commonly known as Blue Crows and Blue Jays. Two of these are known to occur in the woods of the northern provinces of Argentina. 107. CYANOCORAX CHRYSOPS (Vieill.). (URRACA JAY.) +Cyanocorax chrysops+, _Sharpe, Cat. B._ iii. p. 120. +Cyanocorax pileatus+, _Burm. La-Plata Reise_, ii. p. 495 (Uruguay, Tucuman); _Scl. et Salv. Nomencl._ p. 39; _White, P. Z. S._ 1882, p. 602 (Salta); _Barrows, Bull. Nutt. Orn. Cl._ viii. p. 136 (Entrerios). +Cyanocorax tucumanus+, _Cab. J. f. O._ 1883, p. 216 (Tucuman). _Description._--Above black, slightly glossed with purple; head, throat, and breast black, the plumes of the crown forming a crest; nape greyish blue, deepening into purple on the hind neck; above the eye a blue spot; below the eye a second spot and a patch at the base of the lower mandible purple; under surface and tip of the tail creamy yellow; bill and feet black: total length 14 inches, wing 6·3, tail 7·1. _Hab._ Brazil, Paraguay, Uruguay, and Northern Argentina. "This Blue Jay is very common about the woods at Campo Colorado (Salta). It is remarkably tame and inquisitive, and has a great variety of peculiar grating metallic notes. On the sierras of Totoral I likewise met with it; and it is found as far south as Tucuman and Catamarca." (_White._) According to Azara it is abundant in Paraguay and familiar with man, coming a great deal about the houses. The vernacular name there is _Acahé_. 108. CYANOCORAX CÆRULEUS (Vieill.). (AZURE JAY.) +Cyanocorax cæruleus+, _Sharpe, Cat. Birds_, iii. p. 126; _White, P. Z. S._ 1882, p. 603 (Misiones). +Cyanocorax azureus+, _Scl. et Salv. Nomencl._ p. 40.