J. S. Gardner — Revision of the British Eocenes. 469 



classed at Heme Bay as Woolwicli and Eeading Beds. Five of these 

 species become extinct, and seven new ones appear, in the Oldhaven 

 Beds of the Survey'. These seven, and eight of the older species, 

 survived in the London Clay. All the thirty-two species, except the 

 seven intruders towards its close, range throughout the whole Lower 

 Eocene group. The sepai'ation of these purely marine beds into 

 three distinct formations breaks down palasontologically. The fauna, 

 as. a whole, is strictly littoral, and destitute of the Volutes, Cowries, 

 and other tropical shells of the London Clay. Though species are 

 few, individuals are drifted together in immense quantities. The 

 flora is known from several localities, and, like the fauna, consists 

 of few species, all of which are of temperate aspect. They are pre- 

 cisely similar to the so-called Miocene flora of Greenland, containing 

 several of the so-called poplars, etc., but the only plant about which 

 any certainty exists is a plane-tree, rather smaller in fruit and foliage 

 than our introduced species of the present day. 



The Middle Eocene. — This I have suggested should include the 

 London Clay and the Lower Bagshot Series. The London Clay in 

 fact marks such an enormous change both in the area of land and 

 in climate, that it becomes an anachronism to place it with the pre- 

 ceding group. It is the most homogeneous of Eocene formations, 

 and has the widest extent, yet the use of the term " Clay " has I 

 believe induced several errors. At Alum Bay and Whiteclifi" Bay 

 marine sands which belong to it have been placed with the com- 

 pletely dissimilar freshwater sands of the Lower Bagshot, and in 

 the London Basin I believe the Eamsdell Clay to be possibly an 

 overlying mass of true London Clay separated, exactly as a mass is 

 Seen to be at Alum Bay, by beds of sand. The formation is chiefly 

 developed in the east, though it extends to the western extremities of 

 the Hampshire Basin. At Harwich and at Heme Bay, only the lower 

 beds remain, and these, though otherwise almost unfossiliferous, are 

 crowded with rolled and macerated twigs. At Heme Bay and 

 Whitstable, and I believe also on the north side of the Thames near 

 Southend, fruits first make their appearance, though not approaching 

 the vast numbers collected at Sheppey, while passing west the 

 quantity of vegetable matter sensibly lessens. The temperature 

 appears gradually to have increased during its formation, for Nautilus, 

 Volutes, etc., commence to become abundant towards its centre, 

 w^hile its uppermost beds show a marked approach in character to 

 those of the later Eocene. The fruits abound in its centre at Sheppey, 

 and are there of a very tropical character, while in lower parts of 

 the series, as at Swale Cliff, they seem less tropical, an Alder cone 

 never met with at Sheppey being the commonest form. The rich 

 Vertebrate fauna contains three Mammals, a toothed Bird (Odonto- 

 jjteryx toliaptcus) , and an Ostrich ; sixteen Chelonians, two Crocodiles 

 and a Serpent, and ninety species of Fish. Three hundred and 

 fifteen Mollusca, eighty-six Protozoa, twenty-eight Crustacea, etc., 

 complete its known fauna. The flora is probably less rich than 

 has been supposed, not more than twenty-five species being at all 

 common. Including almost unique specimens, the number of dis- 

 tinct forms does not at present, 1 am of opinion, surpass a hundred. 



