GEOLOGICAL FORMATIONS. It seems likely that portions at least of the Nummulitic limestone of Persia may be older than this, as I found amongst the specimens collected by W. K. Loftus from Kirrind on the Turko-Persian frontier and now preserved in the British Museum echinoids whose identity with Arachniopleurus reticulatus D. & S. is hardly doubt ful. This species has been shown by Mr. E. Vredenburg to charac terize beds of Laki age in India; which correspond to lower lutetian. in Europe. No beds of the age of the Ranikot have been definitely shown to exist in any part of Persia, and it is quite possible that this stage is really absent. Lithologically the massive limestones are hardly distinguishable in character from the Hippuritic limestone; perhaps the latter is more crystalline, and it certainly as a general rule is more massive and shows the bedding less plainly. Often an alternation of harder and softer beds in the Nummulitics enables the bedding to be made out easily. A reference to the map (Plate XVII) will show the distribution of the Eocene beds in Southern Persia, as far as I was able to make it out. 19 2. 'Omán.-In 'Omán rocks of Nummulitic age are exposed on the coast to the west and south-east of Muscat. Here they rest uncon formably on the upturned and denuded edges both of the serpentin ous rocks as well as of the Carbo-Triassic series of 'Omán. At the base occurs a pebble bed, which in some places is developed to a thickness of as much as 40 feet, and in others thins off to 4 or 5 feet only, being interbedded with variegated bands of gypsiferous clay or of highly ferruginous sandstone of small thickness. The pebbles consist of the dark blue Carboniferous limestone, of quartz or chert derived either from the Archæans or from the metamorphosed beds of the 'Omán series, and occasionally of the basic igneous rock of the neighbourhood. This pebble bed passes up into a yellow rather sandy limestone, containing nummulites, numerous casts of mollusca, and echinoderms. Near Muscat at Darzeit and at Bandar Jissa a thickness of some 200 feet is exposed. The nummulites found here are N. atacica Leym., N. globulus, Assilina granulosa, and Assilina Leymerii. These are accompanied C 2
