It may be added that a few traces of mammals have been obtained from the English Wealden, among which an incisor tooth foreshadows the rodent type.
The Chloritic Marl in the Wealden district furnishes much phosphatic material, which has been extensively worked at Froyle.
IGUANODON, a large extinct herbivorous land reptile from the Wealden formation of western Europe, almost completely known by numerous skeletons from Bernissart, near Mons, Belgium.
Mantell in the Wealden formation of Sussex, and a large part of the skeleton, lacking the head, was subsequently discovered in a block of ragstone in the Lower Greensand near i Skeleton of Iguanodon bernissartensis.
Beckles in the Wealden cliffs near Hastings; and an accurate knowledge of the skeleton was only obtained when many complete specimens were disinterred by the Belgian government from the Wealden beds at Bernissart, near Mons, during the years 1877-1880.
The southern part of the county is occupied by a portion of the Wealden anticline.
The last Wealden furnace was put out in 1828.
The Cretaceous beds are not extensive, but the Wealden deposits of Bernissart, with their numerous remains of Iguanodon, and the chalk of the district about the Dutch frontier near Maastricht, with its very late Cretaceous fauna, are of special interest.
The broad low tongue of Romney Marsh running out to Dungeness is a product of shore-building by the Channel tides, attached to the Wealden area, but not essentially part of it.
The Chalk occupies all the remaining portion of the south-east of England, save the Wealden area, and extends northward as far as Flamborough in Yorkshire, forming the Yorkshire Wolds, the Lincolnshire Wolds, the Chiltern Hills, the N.
Thereafter, in papers published by the Cambridge Philosophical Society and the Geological Society of London, he entered largely into mathematical inquiries connected with geology, dealing with the effects which an elevatory force acting from below would produce on a portion of the earth's crust, in fissures, faults, &c. In this way he discussed the elevation and denudation of the Lake district, the Wealden area, and the Bas Boulonnais.
In the Wealden of Belgium, for example, specimens of Ferns and Coniferae occur, in the form of lignite, which can be sectioned, like recent plants, with a razor, and exhibit an almost unaltered structure.
Representatives of the Ginkgoales constitute characteristic members of the later Triassic floras, and these, with other types, carry us on without any break in continuity to the Rhaetic floras of Scania, Germany, Asia, Chile, Tonkin and Honduras (Map A, VIII.), and to the Jurassic and Wealden floras of many regions in both the north and south hemispheres.
Species referred on good evidence to the Charophyta are represented by a few casts of oogonia and stem fragments, found in Jurassic and Wealden beds, which bear a striking resemblance to existing species.
Zeilleri from the Wealden beds of Sussex.
In the Wealden strata more slender forms have been found - e.g.
Ruffordia Goepperti, a Wealden type, r3 and probably a member of the Schizaeaceae, has been recorded from England, Belgium, and other European countries, and Japan.
Wealden deposits at Hainaut, Fragment of pinna.
Sarmentosa, is clearly a survival in southern latitudes of a family which occupied Matoni- an important place in the vegetation of the Rhaetic Jurassic and Wealden periods.
The numerous species of fronds from Jurassic and Wealden rocks of North America and Europe referred to Thyrsopteris, a recent monotypic genus confined to Juan Fernandez, are in the majority of cases founded on sterile leaves, and of little or no botanical value.
A few tree-ferns which may be included in this family - such as Protopteris - have been described from Wealden and Lower Cretaceous rocks of England, Germany and Austria.
The Wealden and Jurassic genus, Onychiopsis of England, Portugal, Belgium, Germany, Japan, South Afr i ca and Australia, bears a close resemblance to the recent Onychium (Cryptogamme).
A Wealden plant, Weichselia Mantelli, is worthy of mention as a species of very wide geographical distribution, and one of the most characteristic members of the Wealden flora.
Similarly, the genus Sagenopteris, characterized by a habit like that of Marsilia, and represented by fronds consisting of a few spreading broadly oval or narrow segments, with anastomosing veins, borne on the apex of a common petiole, is abundant in rocks ranging from the Rhaetic to the Wealden, but has not so far been satisfactorily placed.
In most cases we have only the evidence of sterile fronds, and this is necessarily unsatisfactory; but the occurrence of numerous stems and fertile shoots demonstrates the wealth of Cycadean plants in many parts of the world, more particularly during the Jurassic and Wealden periods.
Sphenozamites, chiefly from French localities, which are referred to 1 fronds, which therg is good reason to refer to the Cycadales in the Cycads because of their similarity to the pinnate fronds of Upper Triassic, Rhaetic, Jurassic and Wealden rocks in India, modern Cycadaceae.
II (C. Saportae) is from the Wealden strata of Sussex, and possibly identical with Cycadites tenuisectus from Portugal.
Cycadean stems have been found also in the uppermost Jurassic, Wealden and Lower Cretaceous rocks of England, India and other parts of the world.
The best preserved specimens of the true Bennettites type so far described are from the Lower Greensand and Wealden of England, and from Upper Mesozoic strata in North America, Italy and France.
4, Williamsonia, Wealden, England.
There can be little doubt that the majority of the Cycadean fronds of Jurassic and Wealden age, which are nearly always found detached from the rest of the plant, were borne on stems of the Bennettites type.
Androstrobus Balduini from Bathonian rocks of France; Zamites familiaris, described many years ago by Corda, from Lower Cretaceous rocks of Bohemia, and Androstrobus Nathorsti, from Wealden beds in Sussex.
In Rhaetic, Jurassic and Wealden floras, the Ginkgoales were exceedingly abundant (Map B, G i -G 17); in addition to A, Ginkgodium, Japan (Jurassic).
18, G), characterized by the greater C, Greenland (Lower Cretaceous); D, Siberia (Jurassic); E, _Germany number and narrower form of the segments, which may (Wealden); F, England (Jurassic); H, China (Rhaetic).
And Wealden age, but an abundance of fossil wood (Araucarioxylon) from Jurassic and Cretaceous strata in Europe, North America, Madagascar and elsewhere agreeing with that of recent Araucarieae, in addition to several well-preserved female flowers.
The Abietineae do not appear to have played a prominent part before the Wealden period; various older species, e.g.
Well-preserved Abietineous female flowers have been obtained from the Wealden rocks of England and Belgium, e.g.
This description applies almost equally to the floras of the succeeding Jurassic and Wealden periods.
The change to this newer type of vegetation was no doubt less sudden than it appears as read from palaeobotanical records, but the transition period between the Palaeozoic type of vegetation and that which flourished in the Lower Mesozoic era, and continued to the close of the Wealden age, was probably characterized by rapid or almost sudden changes.
To return to the northern hemisphere, it is clear that the Wealden flora, as represented by plants recorded from England, France, Belgium, Portugal, Russia, Germany and other European regions, as also from Japan and elsewhere, carries on, with minor differences, the facies of the older Jurassic floras.
It was at the close of the Wealden period that a second evolutionary wave swept over the vegetation of the world.
Catalogue of the Mesozoic Plants in the British Museum, (a) "Wealden Flora," pts.
- Tertiary After the Wealden period, and before the deposition of the lowest strata of the Chalk, so remarkable a change takes place in the character of the vegetation that this break Lower must be taken as, botanically, the transition point Cretaceous.
These deposits seem to be equivalent to British Wealden rocks, though in the latter, even in their upper part, no trace of Angiosperms has been discovered.
Wanting Danian Upper Chalk Senonian Middle Chalk Turonian Lower Chalk Cenomanian Upper Green-sand Gault Albian Aptian Lower Green-sand Valenginian Urgonian Wealden Neocomian In the continental classification the deposits from the Gault downwards are grouped as Lower Cretaceous; but in Great Britain there is a strong break below the Gault and 'none above; and the Gault is therefore classed as Upper Cretaceous.
The oldest Urodele known is Hylaeobatrachus Dollo (21) from the Lower Wealden of Belgium.
An unmistakable batrachian of this order, referred by its describer to Palaeobatrachus, a determination which is only provisional, has been discovered in the Kimmeridgian of the Sierra del Montsech, Catalonia (25), in a therefore somewhat older formation than the Wealden Caudata Hylaeobatrachus.