I. I ntroduction . T he magnificent section of Burrington Combe, first studied by Prof. C. Lloyd Morgan, was described in considerable detail in 1905 by Mr. (now Dr.) T. F. Sibly. This author laid down, as accurately as was possible at the time of his publication, the broad zonal sequence of the faunas. The very large amount of research that, during the last six years, has been devoted to the Carboniferous Limestone Series, both in the British Isles and in Belgium, has demonstrated the importance of more detailed lithological investigations and the possibility of tracing the evolution and migration of the great Carboniferous gentes of Corals and Brachiopods. The field-work has extended over several years, and we owe much to the willing assistance of many Bristol geologists, especially to Mr. W. H. Wickes and Mr. H. F. Barke. The series of views illustrate the whole sequence, and are labelled with zonal and faunal indices; the precise points at which important rock-types occur are also marked upon them by means of numerals. II. D escription of the I mportant R ock-Types, arranged Z onally and L ithologically . (S. H. R.) [The traverse is from north to south, the zones being thus encountered in descending order.] ViSÉAN. L ower Dibunophyllum Z one (D 1 ). Extent.—The top of Quarry 1 and the hillside on the north. Thickness.—A thickness of about 20 feet is exposed in the quarry, and perhaps 80 feet beyond it. The D beds exposed consist entirely of fine-grained and crystalline grey limestone. The red coloration, which is as a rule