268 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jail. 23, 



given in a future paper.) The organic remains found here during a 

 very short visit were as under : — 



Cytherea obliqua ? Desk. Teeth of Lamnae. 



Natica glaucinoides } Sow. 



Returning to the main hue of outcrop, we reach, about midway 

 between Maidenhead and Uxbridge, the small village of Hed^erley, 

 immediately to the south-west of which, in a brick-field on the slope 

 of the hill, is a very interesting section first visited by Mr. Morris 

 and myself in 1842, at which time the section was much clearer than 

 I found it last autumn. The abundance and fine state of preserva- 

 tion of the organic remains at this place far surpass anything that 

 we had then, or that I have since, seen in any part of the tertiaries 

 westward of London, excepting perhaps Sonning Hill. The fossils 

 are preserved in large tabular masses of calcareous clayey green sand 

 containing a few rounded flint pebbles, at the base of the London 

 clay, and immediately overlying the mottled clays. (See fig. 13.) 



Fig. 13. — Section at Hedgerley. 



— a. Mixed gravel and clay. 



b. London claj': 1. brown and bluish clay with septaria ; 

 2. brownish clay. Fossils scarce in these beds, which 

 attain a thickness of 35 feet at a short distance south- 

 ward. 



. Blackish clayey sand and green sand, underlaid by flat 

 tabular masses of green sand with a calcareous cement 

 and full of fossils. The small round flint pebbles not 

 numerous. 



Mottled clays — light greenish grey and red. 



The chalk is reached at a depth of 45 feet beneath " c," 



of stratum "c," at Hedgerley. 



Ostrea. 



Pectunculus Plumsteadiensis, Soiv. 

 Panopsea intermedia, Soiv. 

 Pleurotoma, large smooth sp. 

 Pyrula tricostata, Desh. 

 Rostellaria Sowerbyi, Mant. 



, n. sp. smaller. 



Tellina. 



Scalaria. 



Vertebrae of fishes. 



Teeth of Lamnae. 



Wood in fragments. 



A boring Mollusk, probably a Lithodo- 



Organic remains 



Cardium nitens, Sow. 



Plumsteadiense, Sow. 



, n. sp. a. 



Cassidaria striata, Sow. 

 Corbula revoluta, Sow. 

 Cytherea obliqua, Desh. 



ovalis, var. ? Sow. 



Ditrupa plana. Sow. sp. 

 Fusus, large finely striated sp. 



, broad smooth sp. 



Glycimeris ? 

 Modiola elegans, Sow. 

 Natica glaucinoides, Sow. 



Hantoniensis, Pilk. mus. 



Nucula. 



The concretionary calcareous masses have a brown and weathered 

 appearance, and have been here and there bored into by some 

 mollusk. These blocks are hterally full of shells, amongst which 

 the Cardium n. sp. o, Cytherea obliqua, Natica glaucinoides, Nucula, 

 Rostellaria Sowerbyi, and the Ditrupa plana, are most abundant. 

 The shells are well-preserved, soine with their nacre, but, as at 

 Sunning Hill, their substance is rather soft and friable. 



