In a study of the rocks of the eastern end of the Newry Complex, the writer distinguished two contrasted groups of hybrid rocks— (i) the Slievegarron type, and (ii) the Seeconnell type—both of which are intimately associated with biotite-pyroxenite and biotite-peridotite. The Slievegarron hybrids comprise an augite-biotite-diorite series. The typical augite-biotite-diorite (1934, p. 611) is a highly undersaturated rock heteromorphous with certain varieties of orthoclase-basalt and leucite-basanite; it might equally well be described as biotite-essexite-gabbro. No further discussion of these rocks will be undertaken in this paper, but it seems desirable to point out that they should not be confused—as unfortunately they have been—with gabbro-diorite.

During the course of several journeys from the port of Zeilah southwards across the Ban or Plain to Buramo on the Abyssinian frontier, collections were made of characteristic crystalline rock groups in the hope of elucidating to some degree the composition and early history of the district. Permission to publish these notes was kindly given by the Colonial Office.