1865.] TAWKET RH^TIC BEDS AND SUTTON STONE. 73 



tui'al purposes. The beds differ mucla in texture : some are fine- 

 grained white limestones, others are softer and very shelly ; some are 

 yellowish-white, and at the upper part are pale-grey and become gra- 

 dually harder. All these, together with the white conglomerate at the 

 base, I include in the Sutton series : the characters of whiteness and 

 softness are only gradually lost, the pale-grey beds being equally 

 fossihferous, and in fact the top beds differ only by being darker 

 and harder. 



The Sutton series is seen lying on the Carboniferous Limestone 

 along the coast from the mouth of the river Ogmore to the Southern- 

 down clifi's, and is again brought up by a fault at Dunraven, where it 

 forms the Point arching over the Carboniferous Limestone. Between 

 Sutton and West the Carboniferous Limestone is approximately hori- 

 zontal ; and there is apparent conformability between it and the 

 white conglomerate which begins the Sutton series ; further on 

 towards Southerndown the Carboniferous Limestone dips at about an 

 angle of 45°, while the Sutton series is still nearly horizontal : this is 

 also the relation of the beds at Dunraven Point ; immediately after 

 this the Sutton and Southerndown series disappear beneath the Lias 

 and the sea. 



The conglomerate at the base consists of rolled pebbles of Car- 

 boniferous Limestone very numerously imbedded with occasional 

 pieces of chert in a soft, fossiliferous, white matrix. The fossils 

 most abundant in this bed are 



Lima tuberculata, 

 PHcatula intusstriata, 

 acuminata. 



Ostrea laevis, 

 Cardita rhomboidalis, 



Corals. 



The included fragments of Carboniferous Limestone are seen to con- 

 tain SpirifercB, Productce, &c. 



Some of the corals may be derived from the Carboniferous Lime- 

 stone, for that formation here is seen to be full of corals weathered 

 out on the surfaces of the beds by the action of the sea and at- 

 mosphere ; the other species are not derived. This conglomerate 

 is 4 feet thick. 



Above this come the white and pale -yellow freestones ; many of 

 these beds contain shattered fragments of black chert, frequently col- 

 lected together in bands. The source of these abundant chert-masses 

 is probably the Carboniferous Limestone. At Dunraven Point the 

 Carboniferous Limestone is seen to contain bands of this black chert as 

 well as large ramifying spongiform masses. Another noticeable 

 character of the series is the curious sutural junction of many of the 

 beds, the appearance being of miniature basalt-like columns, pro- 

 ceeding from a few inches deep in one bed upwards for the same 

 height into that immediately above ; this is, doubtless, of stalactitic 

 origin; the structure may sometimes be seen passing through a 

 fossil and distorting it more or less. 



The presence and dissemination of Galena through these beds is 

 also to be noticed. Sir H. De la Beche notices it as occurring in 

 the plants of the Lower Lias (sic) here * ; this may probably be in 

 * Loc. cit. p. 273, in note. 



