THE YOUNG NATUKALIST. 



113 



six to eight miles wide, running along the south side of the estuary of the 

 Thames. 



THE THANET SANDS.— This formation is composed of a series of 

 fine light coloured sands, and are well exposed in the Isle of Thanet, from 

 whence they take their name. 



The chief fossils are : 

 Heme Bay. 



Astarte tenera, Corbula requlbiensis, Cucullcea deussata, Cyprina Morresii, 

 C. planala, Cytherea orbicularis, Glycimeris rulupiensis, Modiola aystii, 

 M. Mitchelli, Nucula curvata, Ostera belloracina, Pectuncatus terebratu- 

 laris, Thracia oblata. 



THE WOOLWICH AND READING BEDS. — These beds repose 

 upon the Thanet Sands, and are from 20 to 50 feet thick, and consist of 

 alternations of mottled clays, with sands and pebble beds. They are well 

 exposed at Charlton, Cobham Park, and in cliffs east of Hern Bay. 

 Charlton. 



Cerithium, Fusus, Hydrobia melania, Melanopsis, Neritina, Planorbis, 

 Eissoa, Cyrene, Nucula, Ostrea, Psammobia. 

 Upnor. 



Melanopsis fusiformis, Cyrena tellinella, C. cuneiformis, (7. cor data, Ceri- 

 thium funatum, and sharks's teeth (Lamna elegans.) 

 Woolwich. 



Area depressa, Cerithium funatum, Cyrena depressa, C. iellinella, Hydro- 

 bia Websteri, Melania inquinata, Melanopsis subfusiformis, Ostrea bellova- 

 cina, 0. tenera, 

 Blackheath. 



Cyrena cordata, C. deperdita, C, cuneiformis. 



OLDHAVEN BEDS.— -These are beds of flint pebbles and sand, they 

 are well seen at Oldhaven Gap, west of Eeculvers, and they form the surface 

 of Blackheath and Plumstead Common, and are from 20 to 30 feet thick. 



The following fossils have been found at 

 Charlton. 



Sharks teeth, Auricula, Calyptma, Cerithium, Fusus, Hydrobia, Melania 

 inquinata, Melanopsis, Murex, Natica, heritina, Planorbis, Pseudoliva, 

 Area, Cardium, Cyrena cordata, C. cuneiformis, C. intermedia, Modiola, 

 Nucula. 



THE LONDON CLAY.— This is a stiff blue or grey clay. Under 

 London it is 400 feet thick, but 480 feet in the Isle of Sheppy ; it forms the 

 top of Shooter Hill and the hills round Sydenham ; it also constitutes the 



