Johann Baptist von Spix (1781-1826), author, Plate XXXI, Mycetes stramineus (The Venezuelan Red Howler)
Johann Baptist von Spix (1781-1826), author, Plate XXXII, Mycetes barbatus (The Black Howler)
Johann Baptist von Spix (1781-1826), author, Plate XXXIV, Mycetes discolor (The Red Handed Howler)
Johann Baptist von Spix (1781-1826), author, Plate XXXVII, [Various Skulls of Monkeys]
![Johann Baptist von Spix (1781-1826), author, Plate XXXVII, [Various Skulls of Monkeys]](http://aradergalleries.com/cdn/shop/products/Von_Spix_Plate_XXXVII_large.jpg?v=1519071274)