1853.] FORBES — ISLE OF WIGHT. , 265 



with those of the lower freshwater division of the Headon series, the 

 equally conspicuous and far more important and constant limestone 

 of Bembridge. The oyster-bed that lies immediately above the latter 

 has been constantly mistaken for the " Upper Marine" of Headon ; 

 and in order to account for the greater thickness of the fluvio- marine 

 series at Whitecliff, it has been supposed that the Headon series, like 

 several of the Eocene beds of older date at the same place, has 

 thickened out westward. A close inspection of the Whitecliif sec- 

 tion will show that the whole of the Headon series proper is pre- 

 served of nearly equal thickness at Whitecliff and at Headon ; in the 

 former instance, however, occurring among the vertical or nearly 

 vertical strata; hence, perhaps, one cause of the prevalent error. The 

 •limestones have, it is true, disappeared, but the sequence of beds and 

 of characteristic fossils is the same as at both places, although the 

 inter-marine strata are considerably more dominant at Whitecliflf. 

 What then is the Bembridge limestone? The fossil contents at a 

 glance show that it is the equivalent of the limestone of Sconce Point, 

 which is there seen in a perfectly clear section, resting conformably 

 on strata that lie upon the upper freshwater beds surmounting 

 the inter-marine of Col well Bay and Headon Hill. At Sconce, too, 

 among other very slight remains of the marls surmounting the lime- 

 stones, may be found the characteristic fossils of the lower portion of 

 the thick and important marls capping the limestone at Bem- 

 bridge. These same marls are exposed at low water in complete 

 succession along the shore below Hempstead Hill to the east of Yar- 

 mouth, and are there seen to rest upon the limestone of Hempstead 

 Ledge, characterized in like manner by the peculiar fossils of the 

 Sconce, Bembridge, and Binstead limestones. Above the highest of 

 the Bembridge marls we find at Hempstead a fresh series of beds 

 resting, piled up in succession so as to form the entire thickness of 

 the central portion of Hempstead Hill, and characterized by a fresh 

 set of fossils. Thus do we find that the fluvio-marine Eocenes of the 

 Isle of Wight are more than twice as thick as they have hitherto 

 been regarded, and that the additional beds are of even greater geo- 

 logical importance than those hitherto recognized. 



I venture to propose the following classification and nomenclature 

 for the entire assemblage of fluvio-marine beds of older Tertiary date 

 preserved in the Hampshire basin ; the divisions are enumerated in 

 descending order : — 



A. The Hempstead Series. (Fig. 1, «.) 



The thickness of this division is at least 170 feet. Throughout 

 the beds comjjosing it, three fossils, viz. Cyrena semistriata, var., 

 Rissoa Chastelii, and Melania fasciata, prevail. The second of these 

 is not found lower down. All the species of Cerithium, besides many 

 more mollusks, the Cyprides, and apparently also the vertebrata 

 (especially Hyotherium), and plants found here are peculiar to this 

 group. It may be subdivided into four sections, viz. — 



a. The uppermost or Corbula beds ; marine sands and clays con- 

 taining Corbida pisum, and another species, Ostrea callosa 1, Ceri- 



