348 PROF. S. H. REYNOLDS AND DR. A. VATJGHAN ON [Aug. IQI.I, 



Upper Syringothyris Zone (C 2 ). 



Extent.— ^From Plumley's Den past 'The Cave' to the top of 

 Quarry 3. 



Thickness.— 320 feet. 



In the Avon section this horizon shows a very marked division 

 into an upper series of shales and dolomites, the ' Caninia Dolomites,' 

 and a lower thick band of white oolite, the ' Caninia or Gully 

 Oolite.' In the Burrington section the great thickness of limestone 

 forming C 2 shows no such division, but is throughout very uniform, 

 being almost always oolitic or foraminiferal, or exhibiting the two 

 characters combined. The upper 150 feet or so, as one passes 

 southwards from Plumley's Den, is in the main a very conspicuous 

 white oolite, and an oolitic character is strongly in evidence at 

 the base in the higher beds of Quarry 3 ; but between these points 

 the limestone is rather foraminiferal (see PI. XXVIII, fig. 5) than 

 oolitic, and even in the oolitic limestone foraminifera are very 

 abundant and frequently form the centres for the larger grains. 

 Between l The Cave ' and Quarry 3, finely broken-up crinoid stems 

 form an important component of the limestone. 



The peculiar type of brecciated limestone with penecontem- 

 poraneously rounded fragments, already mentioned as occurring in 

 S 2 and S x (see PL XXVIII, figs. 3 & 4), is met with again at various 

 points (9, 118, 56) in the upper part of o . 



TOURNAISIAN. 



Lower Syringothyris Zone (C v including y). 



Extent. — From the top of Quarry 3, along the ill-exposed part 

 of the hillside to about two-thirds of the way down the Great Scarp. 

 Thickness.— 740 feet. 



The general succession of the rocks of this level is as follows, in 

 descending order : — 

 C 1 (6). Dolomitized limestone. 240 feet. 

 C-l (a). Fine-grained, grey, generally crinoidal limestone. 350 feet. 



7 C Highly fossiliferous, commonly crinoidal limestone, with much chert. 



150 -I Fine-grained, grey, crinoidal limestone, often highly fossiliferous. 

 feet. I This is identical with the ' Petit Granit ' of the Belgian geologists. 



Further Account of the Lithology of the C Beds. 



Although the dolomitization which has taken place at this level 

 is not so marked as it is in the Avon section, it is still by far the 

 most important feature of the upper part of C 1 (see PL XXVIII, 

 fig. 6 & PI. XXIX, fig. 1). The dolomitized rocks 1 clearly were 

 originally crinoidal and foraminiferal limestones containing a large 

 proportion of a calcareous paste or matrix, and it is interesting 



1 Our observations are in close accord with those of Mr. E. E. L. Dixon, 

 Summary of Progress for 1905 ' Mem. Geol. Surv. 1906, p. 48. 



