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.  

Arara hyacinthinus Spix Av. Bras l.t,23 (fig. bona)

Rostrum pro avis mole subparvum, laeve; maxillae culmen rotundatum, ante apicem subsinuatum; mandibula mediocris, pagina antica rotundata, ante apicem recto-truncatum subemarginata; irides albicantes; pedes unguesque nigri; cauda admodum elongata, lanceolata; alae amplae, longae. Longitudo 181/2", caudae 9" 10'", alae 63/4", rostri ad frontem 1" 5"', tarsi 9"', digiti antici externi excluso ungue, 131/4"'. Habitat gregaria in Brasilia versus flumen Amazonum. [Mus. Monac.).