SynopsisIn Part I brief descriptions are given of the goniatite faunas found at horizons in the Scottish Carboniferous succession; and mainly on the evidence of these faunas, the stages of B, P1; P2, E1; and E2 and A are approximately demarcated. No goniatites suggesting the presence of H, R and G have been seen.In Part II descriptions are given of certain species of the following genera: Beyrichoceratoides, Anthracoceras, Cravenoceras, Cravenoceratoides, Girtyoceras, Eumorphoceras, Goniatites, Sudeticeras, Dimorphoceras, Neodimorphoceras and a new genus, Cluthoceras.
It is well known that the dimensions of the ammonite shell conform approximately with the properties of a logarithmic or equiangular spiral. An illuminating account of the logarithmic spiral in its application to the growth of molluscan shells is that given by Sir D'Arcy Thompson (1917, pp. 491–586, and 1942, pp. 748–849). His formula relating the spiral angle of the shell and the ratios of certain linear dimensions must be useful to all interested in shell form in molluscs.
The collection of echinoids, which is the subject of this report, was made by Mr R. A. Farquharson, M.A., M.Sc., F.G.S., Government Geologist, during his survey of British Somaliland in the year 1923–24. The collection was presented by the Colonial Office to the Geological Department of the British Museum, and the Keeper, Dr F. A. Bather, F.R.S., has been good enough to allow me to examine and describe these interesting specimens. I have been fortunate in having beside me for comparison the echinoids from Somaliland in the Hunterian Museum, which were collected by Mr B. K. N. Wyllie, B.Sc., F.G.S., and Dr W. E. Smellie, and through them presented by the Anglo-Persian Oil Company. I take this opportunity of expressing my thanks to Professor Gregory for his interest in the collection and for much kind help.
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