92 Reports and Proceedings — Geological Society of London. 



III.— January 6, 1897.— Dr. Henry Hicks, F.R.S., President, 

 in the Chair. The following communications were read : — 



1. " On the Structure of the Skull of a Pliosaur." By C. W. 

 Andrews, Esq., B.Sc, F.G.S. 



The paper deals with a specimen of the Plesiosaurian known as 

 Pliosaurus ferox, Sauvage, obtained by Mr. A. N. Leeds from the 

 Oxford Clay near Peterborough, and now in the British Museum, 

 and perhaps the finest Pliosaur skull known. It bears a great 

 similarity to Peloneustes philarchus, but there are a number of 

 differences which tend to show that the subject of the present 

 communication is not the skull of an old individual of Peloneustes. 

 Although the teeth of the fossil here described agree precisely with 

 those described by Sauvage from the same horizon at Boulogne 

 under the name Liopleurodon ferox, they differ considerably from 

 those of the Kimmeridge Clay upon which Owen founded the genus 

 Pliosaurus ; they, however, show a distinct tendency towards the 

 typical form, and since the skull and skeleton of the Oxfordian and 

 Kimmeridgian forms are, so far as known, closely similar, the author 

 prefers for the present to follow the British Museum Catalogue in 

 referring them both to one genus, Pliosaurus. 



The author gives a detailed description of the skull which forms 

 the subject of the paper. 



2. " On the Pembroke Earthquakes of August, 1892, and 

 November, 1893." By Charles Davison, Sc.D., F.G S. 



Part I of this paper deals with the earthquakes of August, 1892, 

 of which eleven are recorded, the principal being the third. The 

 author gives an account of the preliminary shocks and after-shocks, 

 and a detailed account of the principal earthquake, describing the 

 disturbed area, the relationship of the earthquake to a north-and- 

 south fault, hading to the west, that of sound to shock, and the 

 occurrence of sea-waves. 



Part II treats of the earthquakes of November, 1893 ; there were 

 four undoubted earthquakes, of which the first was the chief one. 

 Descriptions are given of the phenomena. 



Part III treats of the origin of the earthquakes and their 

 connection with faults ; and the author points out the possible 

 value of the study of earthquakes in supplementing geological 

 surveys. For more than fifty years prior to the earthquakes 

 of 1892-3 there appear to have been no slips of importance along 

 the fault-system of the area. After this prolonged interval of repose, 

 the earlier movements took place along transverse (north-and-south) 

 faults, and the later along longitudinal (east-and-west) ones. The 

 three faults of the latter series which the author connects with the 

 disturbances lie successively one to the north of the other, as if the 

 abrupt displacement of a rock-mass over one thrust-plane impelled 

 the advance of those immediately below. There can be little doubt 

 that the fault-slips of 1892 affected the conditions of stress along the 

 neighbouring transverse fault, so that the displacements along it 

 occurred earlier than they might otherwise have done. 



3. "Changes of Level in the Bermuda Islands." By Professor 

 Kalph S. Tarr. (Communicated by the Secretary.) 



