1850.] 



PRESTV/ICH ON THE LOWER TERTIARY STRATA, 



265 



beds of Woolwich as well as the mottled clays are entirely wanting. 

 Still the physical or palseontological characters are such as to warrant 

 our considering as the basement bed of the London clay the twenty 

 feet of sands immediately underlying the London clay, although there 

 is here no passage between them. This bed is well exhibited in the 

 centre of the cliff east and west of the ravine at Bishopstoke, two 

 miles east of Heme Bay. (See fig. 11.) 



Section near Heme Bay. 



Brown and yellow clay, more or less mixed with 



ochreous flint gravel. 

 London clay ; upper beds of a brown colour, and 

 with a few small septaria covered with vermiform 

 impressions, passing down into laminated dark 

 grey clay, more or less sandy, with carbonized 

 vegetable matter. Traces of Ditnipa plana and 

 of two species of Nummulites occur in the lower 

 part of this clay ; other fossils are extremely scarce. 

 r\. Thin irregular seam of green sand ; feiTuginous 

 clay and a few round flint pebbles, 2 to 3 inches. 

 2. Very light yellow sands with tabular con- 

 creted masses of sandstone and iron sandstone ; 

 these are frequently overlaid by a mass corre- 

 sponding in size of dark clay; very friable 

 shells are irregularly dispersed throughout this 

 bed in small layers and in patches; on the 

 under side of the blocks they are particularly 

 abundant, casts chiefly. 3 & 4. Small flint 

 pebbles with a very irregular series of thin 

 beds of clay and of ferruginous sandstone full 

 of casts of shells. Teeth, vertebrae and bones 

 of fishes of frequent occurrence. 



d. Light greenish clayey sands ; upper surface worn 

 and indented by the pebble bed above. Beneath 

 are some very fossiliferous clayey sands. 



Organic remains of '^ c,' 



A start e. 



Buccinura junceum, Sow. 



Cardiura nitens, Sow. 



Plumsteadieuse, Sow. 



, n. sp. a,. 



Cerithium variabile, Denh. 

 Cytherea obliqua. 



ovalis, var. ?, Sow. 



Cytherea or Cyprina, a large gibbous sp. 



Cyprina Morrisii, Sow. 



Corbula revoluta, Sow. 



Fusus tuberosus ?, Sow. 



~, n. sp. 



Modiola. 



Natica labellata, Lamk. 



in the Heme Bay cliff's. 



Natica glaucinoides, Sow. 



Hantoniensis, Pilk. 



Nucula margaritacea, var. j8, Desk. 



, longer sp. 



Ostrea, small sp. 

 Pectunculus brevirostris, Sow. 



Pluiiisteadieiisis, Sow. 



Pleurotoraa comma, Sow. 



, a second sp. 



Pyrula. 



Rostellaria Sowerbyi, Mant. 



, n. sp. large and striated. 



Scalarja. 



Vertebrae, bones and scales of fishes. 



Teeth of Lamnae. 



The estuary species, it will here be observed, have almost entirely 

 disappeared, and we have a fauna presenting a very close analogy 

 with that of stratum " c" at Sonning Hill near Reading and Claren- 

 don Hill near Salisbury. Still at Heme Bay, and more especially at 

 Boughton and Upnor, the fauna differs in some measure from the 

 one which I consider to be synchronous with it to the westward of 

 London. The bed itself also appears more distinctly separable in 

 mineral character from the London clay. 



We will now return to our starting-point at Pebble Hill, and thence 



