The list of catalogues (pp. 98-101) appended to the general bibliographies is perhaps the most unfortunate exhibit of Petzholdt's selections. His wide experience in this field should have told him the right catalogues to cite. He offers us a strange hodgepodge consisting of one early eighteenth-century catalogue (the _Duboisiana_), a handbook of bibliography, several nineteenth-century catalogues of private libraries, and a few dealers' catalogues. The _Duboisiana_, Michael Denis's _Einleitung in die Bücherkunde_, and Part II of the Libri catalogue (1861) are not hard to justify, but the remaining titles appear to be a random selection. Inasmuch as he devotes almost one quarter of the space to a full-length citation of a part of the Libri catalogue, he should have taken the trouble to find the other parts. Although Petzholdt's list of catalogues interesting to bibliographers has the merit of being more international in scope than most of his lists for special disciplines, he overlooked many large and admirable polymathic catalogues. He does not mention the Thott and Heber catalogues or the _Firmiana_, to name no others. Petzholdt's abundant descriptive and critical comments ensure the _Bibliotheca bibliographica_ of a permanent place on every bibliographer's desk. He expresses an extensive analysis and usually accurate opinion about almost every book that he cites. It did not occur to him to tell the reader the number of titles in these books, but bibliographers have been slow to realize the value of this detail. There are, however, some qualifications of any praise of Petzholdt's comments. His unsympathetic feeling for sixteenth- and seventeenth-century bibliographers leads him to dismiss (p. 7) Teissier's bibliographies of bibliographies with "Virtually worthless today (Gegenwärtig so gut wie werthlos)." His condemnation of Raffaelle Soprani's Genoese biobibliography (pp. 360-361) and Leo Allacci's _Apes Urbanae_ (p. 362) for listing authors by their first names can be properly called naive. In describing Agostino Oldoini's similar book for Perugia (p. 363), he says that this was the usual procedure in the seventeenth century and involved only the inconvenience of consulting an index of last names. These Renaissance bibliographers had inherited this procedure from medieval scholars who knew men by their Christian names and used other designations only when a differentiation of individuals was necessary. Even today a bibliography arranged in this fashion can prove to be a useful tool. The medieval mathematician Richard Suisset, whose last name occurs in various spellings, can be easily tracked down by use of his Christian name. He is not easy to find in a modern book unless one remembers the particular spelling of his name that the author prefers.