The lithological character and sequence of the lower part of the Coal-measures of the Yorkshire Coalfield have been well known since the publication of the memoir by the Geological Survey in 1878. No connected account of the explorations in the equivalent measures of the Derbyshire and Nottinghamshire portion of the coalfield has been written; thus the close correspondence which exists between the lower part of the Coal-measures of Yorkshire and that of Derbyshire and Nottinghamshire is still generally unknown.

The group of intrusions of which this paper treats is a part of a series of intrusive rocks piercing the Carboniferous starta of the Midland Valley of Scotland. As a rule, they have forced their way into the Carboniferous Limestone Series in layers roughly parallel to the stratification. At the surface they stand out as rough, craggy hills, often of considerable elevation, rising abruptly out of the plain of the Carboniferous sediments, and frequently ending off in a vertical escarpment of bare rock. They generally confront, at a distance of 1 or 2 miles, the terraced escarpments of Lower Carboniferous lavas, which bound the Midland Valley on the north, west, and south-west.

Having in a collection of fossils from the Lithographic Stone of Bavaria a Ganoid fish, I consulted Dr. Smith Woodward, and through his kind assistance have proved it to belong to the rare species Pleuropholis lœvissima. The species has hitherto been imperfectly known, the only figure being by Egerton of a comparatively small fish, about the specific determination of which there seems to be some doubt. I therefore think the new specimen worthy of description, and it is shown of half the natural size in the accompanying figure. Nearly the whole of the fish is preserved in the fossil, but the head is shown only in impression. Most of the scales are removed from the near side, and the fins are fragmentary (see Plate XIII).

The necessity of providing a water supply for the town and harbour of Port Sudan has led to an investigation of the district, and some interesting water analyses, relating both to the Valley Fill and to the Maritime Plain, have been made. Through the kindness of Capt. Kennedy, R.E., Director of Public Works, and of Dr. Balfour, Director of the Wellcome Research Laboratories, I am able to quote some of them. The analyses are given on p. 318 and have been made, as indicated, either at the Chemical Research Laboratory, Khartoum, in charge of Dr. Beam (W.R.L., Khartoum), or by Mr. Lucas, Superintendent of the Egyptian Survey Department Laboratory, Cairo (S.D.L., Cairo). A rough map of the district (Fig. 2) shows the positions of the localities from which the samples were obtained.