104 



H. KEEPING AND E. B. TAWNEY ON THE BEDS AT 



are considerably thicker here than at Headon Hill ; their character 

 is very variable even in different parts of Colwell Bay. The 

 Limnasa-limestone has here a rnnch reduced thickness, as mentioned 

 previously. 



Among the other beds we may specially notice the horizon of 

 Cyrena Wrightii : it occurs in the nodular ferruginous sand-rock 

 with Corbicula obovata, also in the sand immediately above the 

 Limna3a-limestone, and again in some of the clays below. Another 

 fossil that we have only observed at one horizon is the C&rithium 

 trizonatum (Morr.) ; it occurs in the pale greenish clays beneath the 

 limestone, occupying only a narrow band in these clays. Equally 

 characteristic is Serpida tenuis (Sow.), which occurs at the same 

 horizon both here and at Headon Hill, viz. in the Upper Potamomya- 

 clay just above the limestone. 



The Paludina-clays at the top are identical with those of Headon 

 Hill at the top of the thick limestones. Measurement by tape here 

 gave 15 feet ; total of the Upper Headon near Cliff End 46^- feet. 



Osborne Beds of Cliff End. — The red and greenish mottled marls 

 of the Osborne series follow. These beds show for a few yards only, 

 and then become hidden under the grass which the engineers have 

 grown on the artificial slopes below the battery. One of us well 

 remembers the numerous little faults (14 are enumerated by the 

 Survey, as cited above) which repeated the Limnaea -limestone. 

 Beyond the battery the Osborne beds form the tumbled cliff ; a 

 measurement is no longer to be made with profit. Mr. Bristow 

 gives 62 feet for the series here. 



III. Pal^ontological Evidence. 



The question now arises, Does the distribution of fossils bear out 

 the separation of the Colwell-Bay and Headon-Hill marine beds 

 and their reference to different horizons ? and does it sanction the 

 notion of the Brockenhurst bed being equivalent to the Colwell-Bay 

 bed? 



Two lists of fossils are laid before us, viz. one which mixes up the 

 fossils from the Brockenhurst, Whitecliff Bay, and Colwell-Bay 

 localities, and the other which gives those from the marine beds of 

 Headon Hill and Hordwell Cliff ; of the hundred forms (in round 

 numbers) which occur in the latter list, it is said (op. tit. p. .150) 

 " less than one half occur at the other three places." 



We may urge at the commencement that it comes rather near to 

 begging the question to mix up Colwell-Bay with Brockenhurst-series 

 localities. We conceive one of the main points in dispute to be 

 whether the Colwell-Bay bed has any more affinities with the 

 Brockenhurst fauna than has the Headon-Hill bed ; and to this sub- 

 ject we shall address ourselves after we have first compared the 

 fauna of the Colwell-Bay and Headon-Hill marine beds. 



The first thing to be done is to separate the faunas of all the 

 localities which are to be compared together ; this we have done in 



