Zoarium incrusting, with a tendency to grow in bands: the general surface stands high and shows no trace of zoœcial boundaries; it is much rumpled, apparently unsysteniatically, but is only broken by the zoœcial peristomes; these are short tubular prominences inclined slightly forwards but bent upwards at the ends so as to end in a plane parallel with the general surface: the apertures are on the whole circular, but very rarely truly so, and occasionally very irregular; they vary in internal diameter from -08 in a small specimen such as Fig. 2 up to -15mm. in a large specimen such as Fig. 3; the peristomes are thick and each has from one to four pores in it; these pores are generally small and round, but occasionally among the larger ones are found definite instances of arrowhead shape which makes it possible that all are avicularian: round the edges of the zoarium there is a fairly complete fringe of simple shallow Membraniporiform zoœcia, with the general surface either ending abruptly above them or sloping gradually down to them.

But while it is difficult to collect fossils in situ in the upper part of the Lower Lias, a very good knowledge of the fauna is obtained from the material which may be collected on the tunnel heaps between Old Dalbyand Saxelby. I have been permitted to study the large collection of specimens from these heaps which are preserved at University College, Nottingham, and the Engineer of the Midland Railway Company gave me leave to make small excavations. The following lists give some idea of the fauna, which contains abundant Ammonites, especially of the genera Tragophylloceras, Polymorphites, and Platypleuroceras. The Foraminifera likewise are unusually interesting; a list of genera identified by Wilson has already been given by Quilter; according to the list given by H. B. Woodward no Textularia-like form is known from the Lias of any other British locality.

The structure of mountain ranges has always been difficult to understand. They often show that peculiarly complicated disturbances of strata have occurred in the process of their formation. Mountain ranges in many stages of dissection are to be seen in various parts of the world; but the better knowledge which their study has furnished us with has not, at the moment, always assisted us in the better understanding of the problem of mountain building.

In the almost complete absence of fossils in the British Keuper there has been a lack of datum-lines in that formation by which we may compare the horizons of different sections. Yet in such a thick and widely spread deposit it is very desirable to have subdivisions enabling us to give the particular part of the Keuper to which a section belongs. In deposits such as the New Red formations too great stress has been laid on lithology, inevitable perhaps in the scarcity of fossils, but a source of grave errors in correlation. For example, Mr. L. J. Wills thinks that fossils found in the Keuper of Warwick have affinity, not with the Keuper, but with the Muschelkalk of Germany. Again, there are strata in the Permo-Bunter of Nottinghamshire which might be mistaken for Keuper Waterstones, if only lithology was considered. Over small areas a band of sandstone with some peculiarities may be used as a datum-line, as in the Arden district of Warwickshire and in Nottinghamshire, but these are of local value only.

There is a regrettable tendency to looseness of thought among geologists on the subject of isostasy. I give no quotations in support of this assertion, firstly because, being always in the form of casual allusions to the principle, they would require long hunting down; and secondly because, if given, they would fasten upon a few individual geologists a criticism which should be more general. The usual form in which the looseness of thought shows itself is in explanations of shallow-water deposits of thickness greater than their depth of accumulation. We are frequently told that such thick deposits result from local subsidence due to the loading of the sea-floor by the great weight of sediment, and reference is made to the principle of isostasy as justifying this explanation.