From Woburn through Ampthill to Potton a more elevated tract is formed by the Lower Greensand.
At Potton, phosphatized nodules may be obtained, and here a hard bed, the "Carstone," lies at the top of the formation.
Potton (2033), Shefford (874), and Woburn (1129) are lesser towns, and local centres of the agricultural trade.
The church of Cockayne Hatley, near Potton, is fitted with rich Flemish carved wood, mostly from the abbey of Alne near Charleroi, and dating from 1689, but brought here by a former rector early in the 19th century.
The Lower Greensand phosphates have been worked, under the name of " coprolites," at Potton in Bedfordshire and at Upware and Wicken in Cambridgeshire.