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TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



The careful zonal work of Mr. S. S. Buckman* Las shown that 

 their age varies from place to place, for they yield an ammonite 

 fauna in which many sub-divisions can be recognized. The 

 Lias, generally speaking, is a clay-formation, and the Inferior 

 Oolite consists chiefly of limestones. In the area considered, 

 a shallower phase characterised by the deposition of calcareous 

 sands set in towards the end of Liassic times and continued 

 throughout part of Inferior Oolite times. But this phase of 

 shallowing and deposition of detrital sandy material passed 

 as a wave southwards, maintaining a peculiar, unusual, and 

 easily recognizable lithology and petrography. The similarity 

 in grade and mineral composition of the sands from Bridport 

 to the Cotteswolds is indeed extraordinary. Expressed dia- 

 grammatically, the sands appear in plan as in Fig. 3, 



COTTESWOLD SANDS 



MIDFORD SANDS 



YEOVIL SANDS 



BRIDPORT SANDS 



Fig. 3. Diagrammatic representation of the time-planes in the Lias- 

 Inferior Oolite Sands, from the Dorset Coast to the Cotteswolds. 



where the belt aa, ft ft is the lithological deposit as it is 

 mapped. 



* Quart. Journ. Geol. Soc, Vol. 45 (1889), p. 440, and Vol. 66 (1910), p. 52. 



