If we take a rapid glance over the volcanic history of the British Isles we find that eruptions having the spilitic facies have occurred repeatedly, over a wide area and on a large scale.

The question of the origin of igneous rocks, their diversity and genetic relationships, represents that fundamental problem of petrography which has been for many years the object of inquiry for petrologists as well as for geologists and chemists. Whilst the amount and scope of detailed observation were growing, the methods of experimental investigation improved, and as the eruptive rocks came to be studied from the point of view of physical chemistry, so the petrogenetical horizon became larger and wider. Thus, on the basis of numerous minute and detailed observations were built broad generalizations that gave rise to new problems.

In all the Regular Echinoids, with the exception of the Cidarids, and in the Irregular Echinoids other than the Clypeastroids and Spatangids, there is a tendency for the ambulacral plates to become crowded together as they approach the margin of the peristome. This is the inevitable result of the continuous formation of fresh plates at the edges of the oculars in the apical system, and their less rapid resorption at the opposite extremity of the ambulacrum. The compression of the ambulaeral plates results in a crowding of the pore-pairs in the peristomial region, and this character seems to serve a sensory as well as a motor purpose.

The following note on the rocks of the shore-line of part of the Gold Coast Colony are a result of a short journey I undertook there in 1910. On that occasion I landed at Cape Coast Castle and travelled westward, staying successively at Elmina, Chama, and Sekondi.