The contents of the volume are distributed as follows: An introduction (ix.-xxiv.) by Dr. Todd is followed by an appendix (xxiv.-xlix.) containing “a number of memoranda, references to authorities, and miscellaneous notes, which have been written by the author, and others, through whose hands the MS. has passed, on the fly-leaves at the beginning and end of each volume”. Many of them are of great interest. Then come the _Testimonia et Approbationes_ (xlix.-lv.) of Flann Mac Egan, Conner McBrody, Dr. Malachy O’Cadhla, Archbishop of Tuam; Dr. Boetius Mac Egan, Bishop of Elphin; Dr. Thomas Fleming, Archbishop of Dublin; and Dr. Roth Mac Geoghegan, Bishop of Kildare. The _Martyrology_ proper follows (1-351) with the Irish text on one page and Dr. O’Donovan’s translation on the other. The notes appended are but few, and serve merely to explain obscurities in the text, to settle the reading, or to correct some obvious mistake. For almost all the notes we are indebted to Dr. Todd himself. A table of the _Martyrology_, compiled by the author, and translated by Dr. Todd, occupies from page 354 to page 479, and is followed by three indexes, compiled by Dr. Reeves, one of persons (485-528), another of places (529-553), and a third of matters (544-566). These indexes, says Dr. Todd, “possess a topographical and historical interest quite independent of their connection with the present work, and are in themselves a most important practical help to the study of Irish history”. What is the value of this work? What position does it occupy among Irish Ecclesiastical documents? It cannot be regarded as an _original_ authority. “It is confessedly a compilation, and of comparatively recent date, having been completed, as we have seen, in the early part of the seventeenth century. But it is a compilation made by a scholar peculiarly well fitted for the task, who had access to all the original documents then extant in the Irish language, the matter of which he has transferred either in whole or in part into the present work, quoting in almost every instance the sources from which he drew his information” (Introd., p. xiii.). The bare enumeration of these sources will serve to show the value of the book. I. _The Metrical Calendar, or Festilogium of Aengus Ceile De_, commonly called the _Felire of Aengus_. Its author was a monk of Tallaght, near Dublin, in the days when Saint Maolruain was abbot, about the beginning of the ninth century. Dr. Kelly of Maynooth has published a translation of a portion of this _Metrical Calendar_ in his _Calendar of Irish Saints_. II. The _Martyrology of Tallaght_. This is a transcript of a very ancient martyrology containing the names of the saints and martyrs of the entire Church, with the Irish saints added under each day. It was composed at the close of the ninth or very early in the tenth century. The Brussels MS. is an abstract of the ancient copy at Saint Isidore’s at