[ 409 ] 

 XLVIII. Proceedings of Learned Societies, 



GEOLOGICAL SOCIETY. 



[Continued from p. 331.] 



December 2, 1874. — John Evans, Esq., F.It.S., President, 

 in the Chair. 



r PHE following communications were read: — 

 -*■ 1. " On the Femur of Cnjptosaurus eumcrus (Sccley), a Dinosaur 

 from the Oxford Clay of Great Gransden." By Harry Govier 

 Sccley, Esq., F.L.S., F.G.S., Professor of Physical Geography in the 

 Bedford College, London. 



The author described this femur as showing a slight forward bend 

 in the lower third of the shaft, and as having the terminal portions 

 wider in proportion to the length of the bone than in any described 

 Dinosaurian genus. He pointed out its differences from the cor- 

 responding bono in Megcdosauras, Iguanodon, and other genera. 

 The length of the femur was stated to be about 1 foot. 



2. " On the Succession of the Ancient Rocks in the vicinity of 

 St. David's, Pembrokeshire, with special reference to those of the 

 Arenig and Llandcilo grouns and their fossil contents." By Henry 

 Hicks, E.G.S. 



In the first part of this paper the author described the general 

 succession of the rocks In the neighbourhood of St. David's from the 

 base of the Cambrian to the top of the Tremacloc group, and showed 

 that they there form an unbroken scries. The only break or un- 

 conformity recognized is at the base of the Cambrian series, where 

 rocks of that age rest on the edges of beds belonging to a prce- 

 Cambrian ridge. 



In the seeond part the author gave a minute description of the 

 rocks, comparing the Arenig and Llandeilo groups, as seen in Pem- 

 brokeshire with each other, and also with those known in other 

 "Welsh areas. 



Each group he divided into three subgroups, chiefly by the fossil 

 zones found in them. 



1. The Lower Arenig was stated to consist of a series of black 

 slates about 1000 feet thick, and to be characterized chiefly 

 by a great abundance of dendroid graptolites. 



2. Middle Arenig. A series of flags and slates, about 1500 feet 

 thick, and with the following fossils — Ogygia scutatrix, O.pd- 

 tata, Ampy.v Saltern, &c. 



3. Upper Arenig. A series of slates, about 1500 feet in thick- 

 ness, only recently worked out, and found to contain a large 

 number of new and very interesting fossils belonging to the 

 following genera — viz. Ill anus, lllcenopsis, Placoparia, Bar- 

 randia, &c. 



4. Lower Llandeilo. A series of slates and interbedded ash, 

 equivalent to the lowest beds in the Llandeilo and Builth dis- 



