Geological Society of London. 93 



Seeley, Esq., E.L.S., E.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 bone in Megalosaurus, Iguanodon, and other genera. 

 The length of the femur was stated to be about one 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 Llandeilo groups and their fossil contents." By Henry 

 Hicks, F.G.S. 



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

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

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

 that they there form an unbroken series. 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 pre- 

 Cambrian ridge. 



In the second 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. pel- 

 tata, Ampyx Salteri, etc. 



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. Xllcenus, Illcenopsis, Placoparia, Bar- 

 randia, etc. 



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

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

 tricts, and containing species of JEglina, Ogygia, Trinucleus, 

 and the well-known graptolites Didymograptus Murchisoni and 

 Diplograptus foliacens, etc. 



5. Middle Llandeilo. Calcareous slates and flags, with the fossils 

 Asaphus tyrannus, Trinucleus Lloydii, Calymene cambrensis, etc. 



6. Upper Llandeilo. Black slates and flags, with the fossils 

 Ogygia Buchii, Trinucleus finibriatus, etc. 



The Arenig series was first recognized in North Wales by Prof. 

 Sedgwick about the year 1843, and was then discussed by him in 

 papers presented to the Society. The Llandeilo series was discovered 

 by Sir R. Murchison previously in the Llandeilo district, but its posi- 

 tion in the succession was not made out until about 1844. The Geo- 



