Ch. XVL] 



SHELL OF THE HEADON SERIES. 



211 



halt-water remains is most conspicuous in some of the central parts of the 

 formation. Mr. T. "Webster, in his able memoirs on the Isle of Wight, 



Fte. 192. 



Fig. 193. 



Planorbis euomphalus, Sow. 

 Headon Hill. a diarn. 



Eelix labyrinthica. Say. Headon Hill, Isle ofWight; 

 and Hordwell Cliff, Hants— also recent. 



first separated the wnole into a lower freshwater, an upper marine, and 

 an upper freshwater division. 



Among the shells which are widely distributed through the Headon 

 series are Neritina concava (fig. 194), Lymnea caudata (fig. 195), and 

 Cerithium concavum (fig. 196). Helix labyrinthica, Say (fig. 193), a 



Fig. 194 



Fig. 195. 



Fig. 196. 



Neritina concava. 

 Headon Series. 



Lymnea caudata. 

 Headon Beds. 



Cerithium concavum. 

 Headon Series. 



land-shell now inhabiting the United States, was discovered in this series 

 by Mr. Wood in Hordwell Cliff. It is also met with in Headon Hill, in 

 the same beds. At Sconce, in the Isle of Wight, it occurs in the newer 

 Bembridge series, and affords a rare example of an Eocene fossil of a spe- 

 cies still living, though, as usual in such cases, having no local connection 

 with the actual geographical range of the species. 



The lower and middle portion of the Headon series is also met with in 

 Hordwell Cliff (or Hordle, as it is often spelt), near Lymington, Hants, 

 where the organic remains have been studied by Mr. Searles Wood, Dr. 

 Wright, and the Marchioness of Hastings. To the latter we are indebted 

 for a detailed section of the beds,* as well as for the discovery of a variety 

 of new species of fossil mammalia, chelonians, and fish ; also for first call- 

 ing attention to the important fact that these vertebrata differ specifically 

 from those of the Bembridge beds. Among the abundant shells of Hord- 

 well are Paludina lenta and various species of Lymneus, Planorbis, 

 Melania, Cyclas, and Unio, Potomomya, Dreissena, &c. 



* Bulletin, Soc. Geol. de France, 1852, p. 191. 



