Wagler managed to keep the various descriptions on the blue macaws separate in this slim volume, which was highly regarded in the early part of the 19th century. I should like to thank Dr. Juliane Diller, Librarian at the Zoologische Staatssammlung in Munich for sending me a scanned copy of the plate below.

42. S. glauca tab XXVI. Ptilosis tota halichlora, pro vario ad lucem objectu in hyacinthinum vergens, remigibus rectricibusque exceptis, latere inferiori nigris, nitentibus; rostrum totum nigrum; macula pone oculos nudiuscula, trigona et mandibulae basis nudae, albo-flavidae; reliqua capitis para toto plumosa. Mas adult.

Guacamayo bleu Azar. Voy. N.273, Macrocercus glaucus Vieill. N. D.2 p.259

Foemina. Mari similis, eodem paullo minor.

Habitus Sit. Hyacinthinae, hac tamen multo minor; diversa a Sit. Spixii statura multo majore, rostri pictura, caet. Lingua nigra, limbo-flavido; pedes unguesque nigri; palpebrarum margo colore floris rorismarini. Longitudo 281/2", caudae 14", alae 131/2", rostri ad frontem 3" 2"’, tarsi 1’, digiti antici externi, sine ungue 1" 8"’, ambitus rostri circa basin 7" 2"’. Habitat in Brasilia (Montevideo) ac in Paraguay, in arboribus cavis, ut dicitur, saepius in fissuris riparum perpendicularium ad fluvios Parana et Uruguay nidificans. (Mus. Berol.).

Observatio. Vide tabulam hujus monographiae psittacorum VI.