182 Reports and Proceedings — 



3. " On some new or imperfectly known Madreporaria from the 

 Great Oolite of tlie Counties of Oxford, Gloucester, and Somerset." 

 By E. F. Tomes, Esq., F.G.S. 



The main object of the present paper, which is supplementai-y to 

 one already published in the Quarterly Journal (vol. xxxix. p. 168), 

 was to describe a section of the Great Oolite at Milton, in Oxford- 

 shire, another at the Lime-kiln quarry near Cirencester, and some 

 outcrops of the same beds in the neighbourhood of Bath, on Farley 

 Down, Combe Down, and Hampton Down, the localities from which, 

 so many of the types of corals described by MM. Milne-Edwards 

 and Haime had been derived. Lists of the corals obtained from 

 particular beds in each of the sections mentioned were given, and 

 several of these corals were described as new, remarks been ap- 

 pended as to a few previously described forms. In conclusion, a brief 

 description was added of the conditions under which the coralliferous 

 deposits in the neighbourhood of Bath had been formed, and of their 

 probable correlation with the Great Oolite strata of Oxfordshire. 



II.— February 11, 1885.— Prof. T. G. Bonney, D.Sc, LL.D., F.R.S., 

 President, in the chair. The following communications were read : 

 . 1. " The Tertiary and Older Peridotites of Scotland." By John 

 W. Judd, F.R.S., Sec.G.S. 



The very interesting rocks known as " peridotites " have been 

 regarded by many petrographers as peculiar to, and, indeed, 

 characteristic of, the older geological periods ; but in the "Western 

 Ibles of Scotland there occur a number of rocks of this class, con- 

 stituting portions of intrusive masses, which the author, in a pre- 

 vious paper, has shown to be the central cores of Tertiary volcanoes 

 of vast dimensions. 



These Tertiary peridotites are most intimately associated with the 

 gabbros and dolerites, the felspathic and non-felspathic rocks passing 

 into one another by insensible gradations, and the rocks of either 

 class being intersected by veins of the other. The peridotites 

 exhibit the same varieties of microscopic structure as the associated 

 gabbros and dolerites, these structures being described under the 

 names of " granitic," " ophitic," and " porphyro-granulitic." 



The felspars, which are rare in the peridotites, are intermediate in 

 composition between labradorite and anorthite ; they rarely, however, 

 exhibit evidence under the microscope of being built up of laminse 

 belonging to different species. The study of the lamellar twinning, 

 which is a common, but by no means universal character in these 

 felspar crystals, points to the conclusion that it has been induced by 

 pressure or strain, like the similar structure in rock-forming calcite. 

 The pyroxenes are represented by many varieties, both of the mono- 

 clinic forms (augites) and the rhombic forms (enstatites), the former 

 being by far the most abundant. The olivines below are, for the 

 most part, highly ferruginous varieties. The spinellids, magnetite, 

 chromite, and picotite occur in these rocks, as do also titano-ferrite 

 and its alteration-products. Among the accessory constituents biotite 

 is the most abundant. 



It was shown that each of the minerals of these rocks is found to 



