2. Essexite. (a) Carskeoch type.—A small boss of essexite, of rather basic type, pierces the agglomerate of the Carskeoch vent, near Patna, Ayrshire. Macroscopically it is light grey, compact, and fine-grained. In thin section it shows a plexus of fluxionally-arranged plagioclase laths of the composition Ab An, the interstices being filled with subhedral augite of a nearly colourless variety, and fresh olivine. Here and there minute angular interspaces are occupied with turbid isotropic matter, the form and arrangement of the particles of which suggest the former presence of nepheline. A few broad plates of pale augite and crystals of olivine interrupt the general trachytoid fabric. Ilmenite and biotite occur sparsely, and a little orthoclase may be detected on the margins of the plagioclases, extending irregularly into the interspaces. This rock has a distinct individuality, and resembles neither the essexites of Lochend and Craigleith in the Lothians, nor the Crawfordjohn type described below. It is poor in alkali-felspars and felspathoids, is devoid of purple augite, and has a well-developed trachytoid fabric.

Among the fossil Cirripedia the species ‘Brachylepas cretacea’ is of extreme interest, since it affords an important connecting link between the pedunculate and sessile forms. Records of its geographical distribution, moreover, show it to have an exceedingly wide range, but up to the present its vertical range appears to be restricted to the zone of Belemnitella mucronata in the Upper Senonian. We owe our knowledge of Brachylepas to Dr. H. Woodward, F.R.S., who in 1868 founded the species B. cretacea on a single valve under the genus Pyrgoma, and in 1901 on a further and more complete specimen established the genus Brachylepas and the family Brachylepadidæ. Attention is now drawn to this species mainly on account of the fortunate find of the remaining valves of the capitulum.