78 NOTES ON THE LEA VALLEY. 



differences in the details, the beds varying in thickness in 

 a distance of a few yards. The general section was as follows : — 



1. Surface soil and clay, 3 feet 



2. Carbonaceous silt, 5 to 1 1 feet. 



3. Pleistocene gravel. Thickness unknown. 



This section, it will be noted, is almost identical with many 



of those exposed in the excavations in the new reservoirs at 



Walthamstow, the three divisions being constant.^ The top 



layer contained no fossils, and in our opinion represents the 



result of the repeated floods of the river since it was confined 



within banks and the marshes drained. 



The carbonaceous silt was a stiff black clay, full of vegetable 



matter, and extremely difficult to wash. 



The vegetable remains were so decayed that it was almost 



impossible to determine any forms, but remains of the elm were 



common. Lenticular patches of moss, often in the condition of 



peat, occurred throughout, the patches being sometimes three 



feet in diameter, with a maximum thickness of eight inches. 



Leaves of the flag {Iris pseudacovus) were very common and well 



preserved. 



Molluscan remains were scarce, and occurred in patches at 



from 7 to II feet from the surface. 



The only vertebrate fossil was a portion of of the horn core of 



a sheep, Ovis aries (Linn). 



We have determined the following species of mollusca : — 



Hygromia hispida (Linn). 



Vallonia pulchella (Miill). 



Helix nemoralis (Linn). 



Limnsea pereger (Miill). 



,, palustris (Mull). 



,, truncatula (Mull). 



Planorbis umbilicatus, Miill. 



carinatus. Mull. 



vortex (Linn). 



,, fontanus (Lightf). 



Bithynia tentaculata (Linn). 



,, leachii (Shepp). 



Valvata cristata, Miill. 



Vivipara vivipara (Linn). 



iT. V, Holmes, " Geological Notes on the new Reservoirs in the Valley of^tha Lea]near 

 Walthamstow." — Essex Naturalist, Vol. xii., pp. 1-16. 



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