On the Evolution of Zaphrentis delanouei in Lower Carboniferous Times

I. I ntroduction . A n attempt is made, in the following communication, to demonstrate the evolution of a small Zaphrentid coral, belonging to a gens of common occurrence in the Lower Carboniferous rocks of Scotland. The simple rugose corals seem to have been strangely neglected by workers on phylogenetic problems. Although suggestions as to the lines of evolution of certain species have been advanced from time to time, no direct proofs have, apparently, been forthcoming. Yet, in some respects, few of the Invertebrata are so well adapted for investigations of this nature. In most of these corals, all the growth-stages of the skeleton are retained intact, and can be studied by means of serial sections cut across the corallum. The one serious difficulty arises from the remarkably sporadic distribution of such fossils or, indeed, of the Rugosa in general —a fact only realized to the full after one has engaged in the systematic examination of a wide area, in search of some particular gens. As a matter of fact, the corals here dealt with are the only ones that range through most of the Lower Carboniferous rocks of Scotland. Even then, they are found on horizons often somewhat widely separated in time and unproductive for long distances. Fortunately, the stratigraphy of the Scottish rocks is so well known, that collections can be made all over the country, from horizons the position of which in the sequence is fixed more or less definitely. Although, therefore, section after section of some particular limestone may