136 Reports and Proceedings—Greological Society of London. 
January 26, 1910.—Professor W. J. Sollas, LL.D., Se.D., F.R.S., 
President, in the Chair. 
The following communications were read :— 
1. ‘On a Skull of Megalosaurus from the Great Oolite of Minchin- 
hampton.” By Arthur Smith Woodward, LL.D., F.R.S., F.L.S., 
Sec. G.S. 
The specimen was discovered and prepared by Mr. F. Lewis 
Bradley, F.G.S., and shows for the first time the skull of Megalosaurus. 
It agrees closely with the Megalosaurian skulls of other genera 
already discovered in the Jurassic and Cretaceous of North America, 
and resembles Ceratosaurus in possessing a bony horn-core on the 
nose. As in the jaws of Jegalosaurus previously known, the pre- 
maxilla of the new specimen bears four teeth; but these teeth are 
so different from those of the typical Jf. bucklandi of the same horizon 
that they prove the Minchinhampton fossil to belong to a distinct 
species. 
2. ‘* Problems of Ore-Deposition in the Lead and Zine Veins of 
Great Britain.” By Alexander Moncrieff Finlayson, M.Se., F.G.S. 
Chemical analyses show traces of lead and zine in several of the 
rock-formations of Britain, but the ores of the veins are concluded 
to be derived, not from the country rock, but from deeper sources, 
probably in the first place by magmatic segregation. They were 
transported in the deeper zones by ‘juvenile’ waters, in which 
fluorme was an important constituent, while in the upper zones, 
especially in limestone districts, underground waters of meteoric 
origin have played a large part. The vein-solutions carried (1) alkaline 
sulphides, which held the sulphides of the metals in solution, and 
(2) alkaline and earthy carbonates. The presence of the latter is 
indicated by the alteration of the wall-rock, which shows a con- 
centration of potash, lime, and carbon dioxide, and a leaching of soda, 
magnesia, oxides of iron, and silica. In limestones, however, the 
chief effects of solution on wall-rock were concentration of silica and 
magnesia. 
The filling of fissures rather than direct replacement of rocks by 
ores has been the chief process, but the calcium of fluorspar has 
been very largely derived from the country rock. Further, much 
local metasomatism is seen, such as replacement of limestone by 
fluorspar, galena, blende, and quartz; and replacement of fluorspar 
by galena. 
The order of deposition determined by microscopic examination of 
polished specimens of ores has been: chalcopyrite, fluorspar, blende, 
gvalena. The galena carries its silver generally in molecular or 
isomorphous combination, except in the case of rich ores, when 
native silver and argentite appear sometimes as threads along the 
cleavage-planes. 
In the effect of the country rock on ore-deposition, the chief 
factors have been: (1) the physical character of the rock and the 
consequent nature of the fissure, (2) its porosity, and (3) its chemical 
composition. ‘The process of deposition involves interchange of con- 
stituents between rock and solutions, even with the least soluble rocks. 
