594 MESSES. GAEDNEE, KEEPING, A]!n) MOXCKTON ON THE 



Series, laying stress on the presence of Oliva Branderi and other 

 Barton types in their fauna, and maintaining that the so-called 

 Cerithium concavum of this zone is really Lamarck's C. pleuroto- 

 moides. From a table appended to his paper, it appears that of 28 

 species 15 are Barton and only 8 Middle Headon. Eliminating 

 those which are common to both these formations, there remained 

 4*34 ^Iq of the Long-Mead-End species common to the Barton Beds 

 and only 21*3 ^/o to the Middle Headon. "As far as fossil evidence 

 is concerned, therefore, these sands are more related to the Barton 

 Beds than they are to the Headon." The fossiliferous beds rise 

 300 yards west of Mead End, and run out at Becton Bunny ; and 

 the unfossiliferous sand rises a quarter of a mile east of Becton 

 Bunny, and disappears beyond Barton Gang. They are the estuary 

 formation of Wright, beds 16 and 17*, and the yellow and white 

 siliceous sands in h of Prestwichf. Their most distinctive fossils 

 may be considered to be Cerithium pleurotomides, Melania Tiordeacea^ 

 and Corhula EdwardsiiX' 



The Barton Series ends at this horizon, where all that is most 

 characteristic of the Barton fauna finally disappears. It is, indeed, 

 at this point, if anywhere in England, that any approach to a sepa- 

 rating line between Eocene and Oligocene can be drawn. 



We do not propose to describe the remainder of the Hordwell section 

 in detail, but as the cliff-line is continuous, we have given a section 

 with measurements of the Headon Beds in fig. 4 , The beds change 

 with the dividing line from brackish to fiuviatile, the junction being 

 a bed of black stratified, lignitic clay, 4 feet thick, containing Pota- 

 momya, Breissena^ Cerithium pyrgatum, &c. Some 17 feet higher 

 up is the Leaf-hed, the exact position of which is not well known, 

 and which we are anxious to take this opportunity of identifpng 

 with regard to forthcoming notices of its fiora. It was known to 

 Dr. Wright as a slate-coloured clay, with impressions of Dicotyledons 

 in considerable number and variety of species, and with fossil fruits 

 and the stems of plants, but no shells. He described it as a well- 

 marked bed, 18 inches thick, rising nearly opposite HordweU House, 

 and running out at Long Mead End. In the Mammal-bed under- 

 neath he had also detected a " small black capsular seed with a cor- 

 rugated integument," as well as Chara medicaginula, Carpolithes 

 ovulum, and C. thalictroides ^ . Wise also describes it as ]8 inches 

 thick II; but where we have made excavations it has exceeded 3 feet. 

 The flora comprises Equisetum, Salvinia, Chrysodeum, Eushes, large 

 Eeather-Palms, Arthrotaxis Couttsice, a leaf known as Popidus Zad- 

 daclii, the latter and some very abundant fruit-spikes being identical 

 with Reading forms. 



* Ann. & Mag. Nat. Hist. ser. 2, vol. vii. (1851) p. 441. 



t Quart. Journ, Geol. Soc. vol. xiii. (1857) p. 108. 



\ Among the Barton species are Buccinum lavatum, Oliva Branderi, Tro- 

 chita aperta. Bulla LamarcJcii, and Cytherea tenuistria ; other forms are Melania 

 hordeacea, Mela7iopsis fusiformis, Ringicula ringens, Nucula tumescens, and Sti^i- 

 gilla colvellensis. 



§ Ann. & Mag. Nat. Hist. ser. 2. vol. vii. (1851) p. 441. 



II Wise, New Forest, 1867, p. 239. 



