284 Reports and Proceedings — Geological Society of London. 



Bolton, Esq., F.E.S.E. (Communicated by George C. Crick, Esq., 

 F.G.S.) 



Sowerby in his " Mineral Conchology " figures two fossils under 

 tbe name of Goniatites Listeri, of which the left-hand figure is 

 clearly G. Listeri, whilst the right-hand one differs considerably 

 from it. The author gives diagnoses of Goniatites Listeri and of a 

 supposed new species, which agrees with the form represented in 

 Sowerby's right-hand figure. This species, noticed by the author, 

 is limited to the shales forming the roof of the " Bullion " or Upper 

 Foot seam of the Lower Coal-measures, whilst G. Listeri ranges 

 from the Lower Limestone Shales to the " Bullion " seam. 



II— May 9th, 1894.— Dr. Henry Woodward, F.E.S., President, 

 in the Chair. 



Mr. Lyddekker exhibited some specimens from a collection of 

 Argentine fossil Vertebrates which he had been allowed to select 

 from the La Plata Museum for presentation by Dr. Moreno to the 

 British Museum. Many of these belonged to types previously 

 quite uni-epresented in the collection of the latter. He also 

 drew attention to his recently published monograph on Argentine 

 Vertebrates, and stated that he hoped these results of his journey 

 to La Plata, under the auspices of the Royal Society, would be 

 regarded as satisfactory. The difficulty he himself had laboured 

 under in endeavouring to understand what had been previously 

 written in regard to the extinct mammals of Argentina was largely 

 due to the absence of satisfactory figures ; and his object had, 

 therefore, been to figure as many specimens as possible on a large 

 scale, in order that others might have an opportunity of judging 

 for themselves, quite apart from his own descriptions and conclusions. 



He had undertaken his previous journey somewhat unwillingly, 

 at the wish of Sir W. H. Flower and Mr. Sclater ; but he had been 

 so interested in what he had seen that he hoped means might be 

 afforded him of repeating his visit this year. 



The following communications were read : — 



1. " Carrock Fell : a Study in the Variation of Igneous Eock- 

 masses.— Parti. The Gabbro." By Alfred Harker, Esq., M.A., F.G.S. 



The paper opens with an account of the general relations of the 

 intrusive rock-masses of the district, and proceeds to deal more 

 particularly with the gabbro, which forms the earliest intrusion. 



A petrological description of the Carrock Fell gabbro is followed 

 by a study of the variations observed in different parts of the mass. 

 The rock becomes progressively more basic from the centre to the 

 margin, passing from a quartz-gabbro with as much as 59^ per cent, 

 of silica to an ultrabasic type with as little as 32^. The latter in 

 extreme cases contains nearly 25 per cent, of iron-ores, partly 

 titaniferous. This is compared with the igneous iron-ores described 

 by Vogt in Scandinavia, etc., and the probable physical cause of the 

 remarkable variation in the gabbro is discussed. 



Other modifications of the gabbro are briefly noticed, due on the 

 one hand to metamorphism of the rock by a somewhat later 



