ZONE OF AMMONITES BUCKLANDI. 65 



Glamorganshire, Somerset, and Dorset. This zone of life is characterised throughout by 

 the prevalence of a number of large Ammonites belonging to the natural group Arietes 

 (von Buch), and by many Conchifera of the genera Lima and Gr^pJicsa. In England it 

 everywhere consists of beds of bluish argillaceous limestone, interstratified with beds of 

 marl, shale, and clay of a similar colour. In some parts of Warwick, Somerset, Dorset, 

 and Glamorgan, this series attains a thickness of 80 feet. 



GloucesfersJtire and SomersetsJdre. — In Gloucestershire it was partly laid open by the 

 deep cutting of the Dean Forest Railway at Highnam, and it is seen in the Lias limestone- 

 quarries near Tewkesbury, and in the natural escarpments at Frethern and Purton-on-the- 

 Severn. In Somersetshire it was fully exposed in making the Great Western Railway be- 

 tween Bristol and Bath, and probably at no point were the several beds of the Lima series 

 better shown than in the cutting at Saltford, seven miles from Bristol. My friend, Mr. William 

 Sanders, made the following section during the execution of the work which, together 

 with his notes on the fossils contained in the different strata, has been kindly communicated 

 by my friend, Mr. Etheridge. This section is of great value, inasmuch as the beds are now 

 partially concealed by debris and vegetation, and the characteristic fossils can no longer 

 be found in their respective beds. 



Section of the Loioer Lias Beds at Saltford, seven miles from Bristol, on the Great 



Western Bailway} 



No. 



59. 

 58. 



57. 



56. 



LiTHOLOGY. Thickness. 



feet. 



Brown gravelly marl IL'O 



Beds of laminated shale and clay 110 



Dark clay, with boulders, and layers 

 of septaria at the top and bottom of 

 the bed, and in the clay between 105 



Gray Lias limestone 100 



Dark shale 



Gray Lias limestone. 



Dark shale 



Gray Lias limestone 



Dark shale. 



Thin limestone-band. 



Dark limestone 



Organic Remains. 



Scales of Tetrago7iolepis and Belemnites acutus, 

 Mill. 



RInjncJwnella variabilis, Schloth. 

 Belemnites acutus. Mill. 



Ostrea Iceviuscula, Sow., Avicula, and Pecten. 

 Ammonites Coiiijljeari,iiovf., and Belemn. acutus,MU.l. 



Nautilus striatus. Sow., Am. Conybeari, Sow., and 

 Belemnites acutus. Mill. 



1 This section shows the relative position of the zones of Ammonites BucJdandi and Am. planorbis and 

 the Avicula contorta series in this part of the county, and affords a good type for comparing these zones 

 in Somersetshire with the same groups in other parts of the south of England. 



9 



