162 



THE POPULAE EDUCATOR. 



TABLE OF THE EOCENE SERIES (JUKES). 



f (Corbula beds. 



| Hempstead J Upper fresh-water and estuary marls, 

 online ] Middle ditto. 



(Lower ditto. 



| Bembridge J Marls and oyster beds. 



Kiddle, or 

 Paris. 



, 



Lower, or 



London. 



( Limestones. 



( St. Helens' sands. 



( Nettlestone grits. 



l_ series. 

 ' Osbome 

 series. 



nv. ^ ( Upper fresh- water. 



Headon I -./-^j, -,, 



< Middle Marine. 



( Lower fresh- water. 

 C Upper Bag-shot. 

 Bagshot ' Barton clay. 



series. \ Bracklesham beds. 

 l_ V. Lower Bagshot. 



f London clay. 



ic clay and sands. 

 et sands. 



Total thickness, 2,555 feet. 



This formation is developed in the neighbourhood of London. 

 If two lines be drawn from a point some twenty miles west of 

 Beading, one passing through Norwich and the other through 

 Canterbury, crossing the channel to the Netherlands, this area 

 of the Eocene will be embraced by them. The north of the Isle 

 of Wight and a triangular patch, extending a little to the 

 north of Salisbury, west to Dorchester, and east to Newhaven, 

 gives the delineation of the other Eocene area. The deposit is 

 shown in the Paris basin, and then is traced south as far as the 

 uppermost bend of the Loire. 



The Thanet Sands. In the Hampshire area, the Eocene clay 

 often rests on the chalk ; but in the Isle of Thanet, between 

 Herne Bay and the Eeculvers, appears a bed of sand some 

 seventy or eighty feet thick, which contains Pholadomya, 

 Cyprina, Gorbula, and Scalaria. The true position of this bed 

 has been proved by Mr. Prestwich to be between the chalk and 



The Woolwich clays, which were evidently deposited by a 

 great river emptying itself into the Eocene sea near the present 

 site of Woolwich. From the mixture of marine, brackish, and 

 fresh-water shells, it appears that now the fresh-water and now 

 the salt-water occupied the estuary ; and these changes could 

 not have been slow, for the fresh-water mollusks are frequently 

 found in their natural positions, indicating that they were 

 killed where they lived, and have never been since disturbed. 

 As the Woolwich clays are traced inland, they bear more and 

 more evidence of the presence of fresh water, while, following 

 them in the other direction, they show that the waves of the sea 

 beat upon a shore not far off, and the clays contain the fossils 

 of a marine fauna. 



The London clay, which immediately overlies the last deposit, 

 is of deep-sea origin. It consists of bluish or brown clay, very 

 tenacious, and sometimes containing those septaria, of which we 

 have before said Roman cement is made, though from its fine- 

 ness, and the thickness of its bed, it must have been deposited 

 in the quiet depths of the deep sea ; yet land must have been 

 in the neighbourhood, for the teeth and bones of crocodiles, the 

 eggs of turtles, and the fruits of palms, have been found in the 

 London clay. The deposit reaches its greatest thickness about 

 the Isle of Sheppey ; it gradually thins out to the east, being 

 scarcely represented in Belgium, and not at all in France. The 

 fossils are numerous, and, as may be seen from those which are 

 figured, are nearly approaching to present forms. For instance, 

 Leda amygdaloides (Fig. 135), Naiitilus ziczac (Fig. 136), Voluta 

 nodosa (Fig. 137), the Cryptodon angulatum (Fig. 138). 



The Bagshot sands occupy extensive districts in the neigh- 

 bourhood of Bagshot, Aldershot, and in the New Forest in 

 Hampshire. In the basin of the Thames they are the upper- 

 most members of the Eocene group, all above them having 

 suffered denudation ; but in Hampshire, having been tilted up 

 at an angle, they were protected from being exposed by having 

 the superincumbent beds swept off. The Bagshot and Brackles- 

 ham beds are of sand, clay, and limestone, usually soft, though 

 now and then sufficiently hard for building material. 



Though soft beds have not the power of preserving fossils 

 with great care, yet there are some in these beds of much inte- 

 rest. It is here we first meet the Nummulite, a foraminiferous 

 shell, that is, one perforated with holes, from which issued 

 filaments, or roots, which bestowed upon the class the name of 

 Ehizopods, or radiate animals. The word mimmulite is coined 



from nummus, money, because the shells are small discs, thicker 

 in the centre than at the edges ; when the interior is laid open 

 it is found to be spirally chambered (Fig. 139). These creatures 

 are almost peculiar to the Eocene, very few being found in the 

 lower Miocene ; and so restricted are their species, that the 

 lower Eocene may be divided into three sections, according to 

 the species of nummulites they contain. The Nummulites 

 variolaria characterises the upper beds ; Nummulites Icevigata, 

 is found in the middle beds, whilst the lower contain solely the 

 Nummulites planulata. 



The nummulite life was vast and profuse. The limestone 

 rocks formed by these shells are found stretching in an 

 almost unbroken chain from the west of Europe to India. To 

 quote Lyell, " The nummulitic formation often attains a thick- 

 ness of many thousand feet, and extends from the Alps to 

 the Carpathians, and is in full force in the north of Africa, 

 as, for example, in Algeria and Morocco. It has also been 

 traced from Egypt, where it was largely quarried of old for the 

 building of the pyramids, into Asia Minor, and across Persia 

 by Bagdad to the mouths of the Indus. It occurs not only in 

 Cutch, but in the mountain-ranges which separate Scinde from 

 Persia, and it has been followed still farther eastward into 

 India, as far as Eastern Bengal and the frontiers of China." 

 This is a remarkable example of uniformity of life, for many of 

 the same species are common to France and Cutch ; and the 

 vast accumulation of organic life exhibited in this Eocene 

 deposit is perfectly incalculable. 



Of the other fossils contained by these beds we figure some. 

 The Venericardia planicosta (Fig. 140), Pleurotoma attenuata 

 (Fig. 141), Turritella multisulcata (Fig. 142), Conns deperditus 

 (Fig. 143). In these beds are found many sharks' teeth; and, 

 not having given any previous drawings of these fossils, we 

 here add some specimens (Figs. 144, 145, 146). 



The Barton clay and Upper Bagshot sands present a thickness 

 of some 500 feet. The former deposit has yielded upwards of 250 

 marine shells. The Chama squamosa is particularly plentiful. 



The Headon series, which are the centre of the middle Eocene, 

 may bo seen at the east and west extremities of the Isle of 

 Wight. As our table indicates, the upper and lower beds are 

 of fresh-water origin, while the sea seems to have made the 

 water brackish during the deposition of the middle strata. The 

 Planorbis enomphalus (Fig. 147) characterises the fresh-water 

 deposits, while the Potamomyaplana and Cerithium mutabile are 

 found in the brackish deposits. There is an interesting shell, 

 the Helix labyrinthica, found in this deposit, which is now 

 living on the land in the United States. The Headon series 

 occupies some 200 feet. 



The Osborne series, which are the uppermost members of the 

 middle Eocene, supply the Nettlestone grit, which is nsed for 

 building-stone at Ryde. They are also of fresh-water and 

 brackish origin, but are not more than seventy feet thick. They 

 contain marked species of Paludina, Melania, and Melanopsis, 

 and frequently the seeds of the fresh-water plant, the Chara. 



The Bembridge series is the lower member of the upper 

 Eocene. The beds, which are marls, clays, and fresh-water 

 limestones, reach a thickness of 115 feet. In these beds were 

 first discovered the fossil remains of the Palceotlierium, the 

 extinct mammal which Cuvier completed from a partial skeleton 

 found in the Paris basin. The correctness of the great 

 naturalist's surmise has been proved by many fossil remains of 

 the creature which have been since found. It was about four 

 feet high (Fig. 148). Of the other fossils the beds contain these 

 were the chief : Planorbis discus (Fig. 149), Bulirnus ellipticus 

 (Fig. 150), Lymnea longiscata (Fig. 151), Ghara tuberculata 

 (Fig. 152). 



The Hempstead beds are at the top of the Eocene ; they used 

 to be classed at the bottom of the Miocene. They take their 

 name from a hill near Yarmouth, Isle of Wight. At their base 

 is the "black band," so called because of its colour, from the 

 presence of carbonaceous matter. It is a marl deposited from 

 a fresh-water estuary. Two other deposits, scarcely so thick, 

 succeed it, each distinguished by its fossils, and the whole is 

 surmounted by the Corbula beds, which consist of marine sands 

 and clays, which are characterised by the abundance of the 

 Corbula pisum (Fig. 153), which are also found in the Barton 

 beds. 



The Paris basin is a depression in the chalk in which the 

 Eocene beds have been deposited. The beds mainly correspond 



