and Marlborough Railways. 



173 



mm 



that the sponge bearing beds are at from 20 to 

 30 feet below the junction of the TJpper-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 "VVoodborough 

 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 (Polypothecia 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 var3'ing from a mixture 

 of greensand and chalk pebbles with a little 

 clay, to a strong blue clay. The claj'ey 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 

 1 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 



