incunabula (Ĭn´kyŏŏnăb´yŏŏlə), plural of incunabulum [Late Lat.,=cradle (books); i.e., books of the cradle days of printing], books printed in the 15th cent. The known incunabula represent about 40,000 editions. The books include products of more than 1,000 presses, including such famous printers as Gutenberg, Jenson, Caxton, and Aldus Manutius and give evidence as to the development of typography in its formative period. These books were generally large quarto size, bound in calf over boards of wood, decorated with red initials (rubricated) and ornamental borders, and carrying a colophon but no title page. Notable European collections of incunabula are in Paris, London (British Museum), Oxford (Bodleian Library), Vienna, Rome, Milan, Brussels, and The Hague. Notable American collections are in Washington, D.C. (Library of Congress), New York City (Morgan Library and others), Providence (John Carter Brown Library and Annmary Brown Memorial), San Marino, Calif. (Henry E. Huntington Library), and in the libraries of Harvard and Yale Univ. For an introduction to incunabula and a guide to further study, see Margaret B. Stillwell, Incunabula and Americana 1450–1800 (2d ed. 1961).