BURMEISTER (German). Los Caballos Fosiles de la pampa argentina. - Die fossilen Pferde der Pampasformation. Buenos Aires: La Tribuna, 1875; Buenos Aires: La Universidad, 1889. - Two large folio volumes, 490 x 345 and 515 x 354: VIII, 88 pp., 8 plates; VI, 65 pp., 4 plates. Publisher's black cloth-backed boards, printed label on front boards. Very rare first edition of these two works by the Prussian-born Argentine naturalist Hermann Burmeister (1807-1892), director of the Buenos Aires Museum of Natural History and professor of natural sciences at the National University of Córdoba. The first volume, published in 1875, was commissioned by the Argentine government for the 1876 Philadelphia World's Fair. Wishing to enhance the value of the museum's South American fossils, Burmeister proposed this project on the fossil horses of the Argentine Pampas, comparing in detail the complete skeleton of an extinct horse with the remains of three other species of the same equine group. The second volume, published almost 15 years later, is a supplement to the first. Published for presentation at the Paris International Exhibition in 1889, it contains descriptions of new parts of the horses described in 1875, as well as some of the Buenos Aires Natural History Museum's most important acquisitions of rare and unknown fossils. Both books are printed on two columns, in Spanish and German. They contain a total of 12 large black lithographs printed in Berlin, 8 in the first, drawn by Burmeister himself, and 4 in the second, drawn by Swiss painter Adolph Methfessel (1835-1909) under the author's direction. "Burmeister's and Methfessel's drawings were technically hyper-realistic and highly appreciated by the scientific community of the time. The plates printed in Buenos Aires from these lithographs made in Berlin were so finely drawn that they resembled photographs." (website: hermanburmeister.blogspot.com). Today, it is rare to find the two volumes together. Soiled boards. The boards of the first volume are loose, the spine of the second is badly damaged. Corners dulled. Some foxing in first volume. The interior of the second volume is very well preserved, with no foxing.