After the lapse of nearly three generations the _Bibliotheca bibliographica_ (1866) by Julius Petzholdt (1812-1891) is still a standard bibliography of bibliographies. Its position will doubtless remain unchallenged. More recent works--notably Theodore Besterman, _A World Bibliography of Bibliographies_--contain more titles and naturally include those published after 1866, but Petzholdt's critical comments and careful collations are still indispensable. The _Bibliotheca bibliographica_ deserves its reputation for its great merits. It also owes this reputation to some extent to Petzholdt's position as head of the famous library at Dresden with a long and honorable bibliographical tradition,[148] his editorship of a successful journal of library science, his standing as the author of professional handbooks, and, last but not least, his vigorous condemnation of other bibliographies. Petzholdt's self-assurance now and again arouses resistance, and leads one to judge him as severely as he judged others, but the _Bibliotheca bibliographica_ will remain a landmark in bibliographical history. Petzholdt's _Bibliotheca bibliographica_ is noteworthy for its extent, its careful organization, its detailed collations, and its useful critical comments. We must nevertheless admit some qualification of all these merits. In extent, Petzholdt falls short of his predecessor Pie Namur. Namur had in 1838 cited 10,236 titles. Many of these did not, to be sure, fall within the limits set by Petzholdt for his work. A generation later Petzholdt cited only an estimated 5500 titles (I take the figure from Besterman). He achieved this figure by excluding many old bibliographies (chiefly works of the seventeenth century), disregarding bibliographies published as journal articles, and including antiquarian catalogues and a few catalogues of private libraries. Although completeness is desirable, it is also unattainable. A comparison in terms of numbers is not very important.