AREA OF THE WEALDEN. 
319 
Vicarya Lujani, De Verneuil.* 
Wealden, Puiifield. 
showing continuous ridges as 
in Nerincea. 
Wealden beds are given as the * Fie:. 297. 
fresh-water equivalents of the Ma¬ 
rine Neocomian. The highest part 
of'them in England may, for rea¬ 
sons just given, be regarded as Up¬ 
per Neocomian, while some of the 
inferior portions may correspond in 
age to the Middle and Lower di¬ 
visions of that group. In favor of 
this latter view, M. Marcou men¬ 
tions that a fish called Aster acan¬ 
thus granulosus^ occurring in the 
Tilgate beds, is characteristic of the 
lowest beds of the Neocomian of 
the Jura, and it is well known that 
Corbula alata^ common in the Ashburnham beds, is found 
also at the base of the Neocomian of the Continent. 
Area of the Wealden .—In regard to the geographical ex¬ 
tent of the Wealden, it can not be accurately laid down, 
because so much of it is concealed beneath the newer marine 
formations. It has been traced about 320 English miles 
from west to east, from the coast of Dorsetshire to near Bou¬ 
logne, in France; and nearly 200 miles from north-west to 
south-east, from Surrey and Plampshire to Yassy, in France. 
If the formation be continuous throughout this space, which 
is very doubtful, it does not follow that the whole was con¬ 
temporaneous ; because, in all likelihood, the physical geog¬ 
raphy of the region underwent frequent changes throughout 
the whole period, and the estuary may have altered its form, 
and even shifted its place. Dr. Dunker, of Cassel, and H. 
von Meyer, in an excellent monograph on the Wealdens of 
Hanover and Westphalia, have shown that they correspond 
so closely, not only in their fossils, but also in their mineral 
characters, with the English series, that we can scarcely hes¬ 
itate to refer the whole to one great delta. Even then, the 
magnitude of the deposit may not exceed that of many mod¬ 
ern rivers. Thus, the delta of the Quorra or Niger, in Afri¬ 
ca, stretches into the interior for more than I'ZO miles, and 
occupies, it is supposed, a space of more than 300 miles along 
the coast, thus forming a surface of more than 25,000 square 
miles, or equal to about one-half of England.f Besides, we 
know not, in such cases, how far the fluviatile sediment and 
organic remains of the river and the land may be carried out 
from the coast, and spread over- the bed of the sea. I have 
* Foss, de Utrillas. 
t Fitton, Geol. of Hastings, p. 58, who cites Lander’s Travels. 
