and Marlborough Railways. 



173 



that the sponge bearing beds are at from 20 to 

 30 feet below the junction of the Upper-green- 

 sand and Chalk, being at a corresponding 

 height to the sponges at Savernake. There is 

 considerable difference in form and texture 

 between the Savernake and the Woodborough 

 sponges. The lobed forms (Hallirhoa costata) 

 are common at Woodborough, and rare at 

 Savernake, and the same may be said of Poly- 

 pothecia agariciformis, while the forms common 

 at Savernake do not occur, or are rare at Wood- 

 borough. Funnel-shaped sponges like Chenen- 

 dospora subplena (Michelin plate 41, fig. 1), 

 and Chenendopora expansa (Polijpothecia expansa 

 of Benett), are common, some of them being as 

 much as 18 inches across. There is a general 

 similarity between the sponges of Woodborough 

 and Warminster. 



After passing through some shallow cuttings 

 in the Upper-green-sand near Beechingstoke 

 and Patney, we come to Patney marshes, where 

 the surface for two miles along the Railway 

 is covered with a drift varying from a mixture 

 of greensand and chalk pebbles with a little 

 clay, to a strong blue clay. The clayey nature 

 of this drift appears to increase as we approach 

 the turnpike road leading from Devizes to Salis- 

 bury, where it is used for brick- making. 



In the cutting near Stert, there is a very 

 i good section of a fault which has thrown up the 

 ; upper beds of the green-sand about 30 feet. 

 As we pass through the cutting from the east, 

 we come successively on higher beds of the 

 Upper- green-sand, till we reach the transition 

 beds, and the chalk marl. There is then a 

 fault, or rather a succession of faults, and the 



