36 Mr. Henry Walker s Lecture : 



derms and deer that have been excavated from the same 

 spot. These identical molhisks, remember, were the con- 

 temporaries of the mammoth in Britain ! They hved in 

 the waters which the mammoth frequented, as they have 

 since shared his grave for thousands of years. We will 

 consign these precious little relics to the small chip boxes 

 we carry with us for the purpose, and will label them at 

 home with name and place of discovery. 



This fresh-water mollusk, Cyrena fluminalis, has never 



been known in British rivers within the historical period. 



It is now to be found in the more tepid waters of the Nile, 



whither it must have retreated ages ago, when physical 



changes of great importance to the biological world began 



to take place in Britain. It is also to be found in certain 



streams of central Asia. The visitor to the Uphall pits at 



Ilf ord will have no difficulty in securing specimens of Cyrena 



fluminalis for his cabinet. The layer which crops out from 



the wall on all sides as we stand in the pit is suggestive of 



a large colony of happy mollusks who found here a good 



feeding-ground in olden time. A further examination shows 



that some of them were drifted here in the 2^ost-mortem 



stage of their history. The geologist will find shells of 



Unio and Anodon as well as of Cyrena at Ilford. And he 



may find land shells (also of the mammoth period), as well 



as the fresh- water shells we have mentioned. The pretty 



helix of the woods {Helix nemoralis), known to Saturday 



afternoon ramblers in Epping Forest, is sometimes found 



in these elephant beds at Ilford with colour-bands looking 



almost as fresh as we may see them in their living 



descendants in the hedgerows of to-day. 



But suddenly an alarm is given. We are not to invade 

 these sacred haunts of ancient life with impunity. The 

 aborigines of the country have been gradually closing in 

 upon us unseen. They now appear, some of gigantic form, 

 looking down upon us exultingly from the brink of the pit. 

 We are fairly caught — outflanked and surrounded by a 

 wily foe. Not an instant is to be lost. With great presence 

 of mind Sir Antonio, our leader, advances with dignified 

 mien to parley with the chief. It is an anxious moment. 



