I don't know whether this specific work is considered to be valid, but here are the general rules. Rarity and anonymous publication are not obstacles to the validity of da Costa's publication, but inconsistent use of binominal nomenclature may be. Anonymous publication was allowed before 1951 (ICZN, Art. 14). It is now banned. Present rarity of a work is not an obstacle to valid publication, though the work must have been "issued publicly for the purpose of providing a permanent scientific record", obtainable (at least in principle), and produced by printing or some other method that "assures numerous identical copies" (Art. 8). There are examples of works that were printed in large numbers, but whose edition was destroyed by fire (bombing) before most of the copies could be distributed. There is even one case where a malacologist (Isaac Lea) is said to have bought up and destroyed most of the edition of a major work by his rival (Timothy Abbott Conrad, a distant relative of R. Tucker Abbott). This work is very rare in its original edition (about 15 or 20 copies are known), though the Paleontological Research Institution has reprinted it twice and the latest edition is still in print. The species named in these publications are valid despite the rarity today of the original edition. There is no threshold number of copies that constitutes "publication", but I would question whether an edition of only ten copies is enough. For valid publication, an author must consistently apply the principle of binominal nomenclature in that work. In works published before 1931, the author is given the benefit of the doubt if he or she uses generic names by themselves without adding specific names or at least the noncommittal abbreviation "sp." (Art. 11). Also, if a book index published before 1931 is consistently binominal, then it can be accepted as valid even if the remainder of the book is not. Of course, subspecies are allowed under binominal nomenclature, even though this results in three names. After 1930, the rules are stricter. Andrew K. Rindsberg Geological Survey of Alabama