PRESTWICH FOSSILIFEROUS IRONSANDS, N. DOWNS. 327 



Fig. 4. — Diagram-section of the Ironsands in their original hori- 

 zontal position. 



t^ffS^iMWWr^^^M f> Yellow sands*, passing down into 



pjjjjil =2 ' ^EJ e > Light-red sand and clay. 



l~: : ~}^^^y^^^i\ d ' I Greenish and yellow sands, with a subordinate seam 

 i^^&^^^l^^^' jr> | of ironstone, c, and some flint-pebbles. 



V : ■_ ,. r " " : " "-- 



Wm SB a, Chalk-flints m Clay. 



Apart from the great scarcity of shell-impressions, the ironstones 

 in this pit are precisely similar to those in the Lenham pit ; and it is 

 to be observed that there also only portions of the ironstone contain 

 fossils. Amongst the fossils sent me by Mr. Jones was a specimen 

 of a large Terebratula ; and, when afterwards at Lenham, I was for- 

 tunate enough to discover another tolerably perfect cast, and it sud- 

 denly struck me, from this and other fossils, that it might be the large 

 Crag species, both from its size and general appearance, and from the 

 absence of any species of that magnitude in our Eocene series. On 

 hastening to compare it with the figures in Mr. Davidson' s Monograph, 

 I found that it bore the closest resemblance in figure and size to the T. 

 grandis. I again examined the other fossils, but, with the exception of 

 the impression of a Scalaria, which resembled the S. subulata, I could 

 obtain no satisfactory result. In the summer of 1856 I made another 

 visit to Lenham, and found, in addition to former species, a large 

 Mya-shaped shell f, also different to any of the Lower Tertiary fossils 

 with which I was acquainted, and reminding me of a Crag species. 

 On mentioning these facts to Mr. Searles Wood, he kindly undertook 

 to examine the specimens, and has favoured me with the appended 

 report (see p. 333). 



I must confess to hold a stronger opinion on the subject than Mr. 

 Wood, for there are collateral circumstances which greatly strengthen 

 my belief of these beds belonging to the Crag, little as I was pre- 

 pared to meet with the Crag at such an elevation and such a di- 

 stance from the main mass. In the first place, I know of no Eocene 

 strata in the London Tertiary area quite like this deposit in its litho- 

 logical structure. Secondly, no London Clay or Lower Tertiary strata 

 contain any Terebratula that can be compared to the T. grandis, or 

 a Lutraria like the specimen from Lenham ; whilst no Echini with 

 club-shaped spines, nor Emarginuloe, Mactrce, nor Nassce have 

 hitherto been met with in the London Clay, or in the beds of 

 sand beneath it ; again, Bryozoa, which are common at Lenham, are 



* These appear in other places to pass upwards into loamy yellow sands with 

 subordinate seams of ironstone and some irregular beds of clay. Some slightly 

 mottled clays above Otford appear to me to belong to this group, although much 

 resembling the mottled clay of the Reading series. It is a question also whether 

 a few sandstone-blocks are not occasionally concreted in these sands. 



f Probably the Lutraria elliptica. 



