The principal descriptions and figures of the Ordovician and Silurian brachiopods of the Girvan district are found in Davidson's Monograph on the British Fossil Brachiopoda, completed about thirty years ago, and issued by the Palæontographical Society. The third volume of this work (published 1866–1870), and the Supplement to the fifth volume (published 1882–1883), dealing with species from Ordovician and Silurian beds, contain descriptions of many Girvan forms, but not apart from those occurring in other British localities. No independent and comprehensive treatise on this group as represented in the Girvan area has been published, though many short papers have dealt with a few species or portions of the fauna. Especially noteworthy are the papers and works by M'Coy and Salter, mentioned in the list at the end of this memoir.

The extensive series of specimens of members of the Hyolithidæ which Mrs Elizabeth Gray has collected from the Ordovician and Silurian beds of the Girvan district, and submitted to me for investigation, forms the basis of the following memoir.Through the kindness of Dr John Horne and Professor J. W. Gregory, special facilities have been afforded me of examining the other Scotch examples in the Geological Survey Collection, Edinburgh, and the Museum of Glasgow University. My thanks are also due to Dr F. L. Kitchin for the opportunity of studying the specimens in the Jermyn Street Museum.

No abstract

It is useful from time to time to take stock of our knowledge in connection with such a geological problem as that of the fauna of the Bokkeveld Beds, so that we may ascertain to what stage in the process of its elucidation we have arrived, and may note the direction in which the evidence is pointing. An indication of the principal gaps in our knowledge may also be obtained in this manner, and new suggestions as to the more promising lines of investigation. The conclusions arrived at from such a survey may be employed tentatively as working hypotheses, but it may be premature to base upon them confident generalisations. Approaching the question of the composition, relations, origin, and distribution of the Bokkeveld fauna in this spirit of caution and with the foregoing objects in view, we find firstly that a considerable advance has been made in our knowledge of it and allied faunas during the last few years. The researches of Ulrich, Kayser, Clarke, Katzer, Thomas, and others in South America have given us an immense amount of fresh information on the Devonian faunas of that continent, and the South African fossils themselves have been studied by Lake, Schwarz, and the author. Their general poor state of preservation is a matter of regret, but the increase in the material available has cleared away some of the difficulties met with by Salter and other previous workers. Much undoubtedly remains to be learnt from work in the field, and we may expect further yields of new species from different localities in the immense area still to be explored.

The conspicuous relations of the brachiopod fauna of these heds to that of the Lower Devonian in South America have frequently been pointed out, and may be summarised as follows:—(1) In the Falkland Islands the following South African species are found (12):—