408 
OOLITIC FOSSILS. 
Tlie Lower Oolites display the advent of the genera Melania 
and Corhicuht, unknown in earlier formations in England, comprising 
rei)resentatives as ennmerated : 
MEL.VXIIU.E. 
Melania incrmis Tate, 
Lejito.ris troc/i ifortnis Tate. 
PALUDESTRIXID.K. 
Paluelcfitrina calcdonica (Tate), 
jn-artirsor (Saiidberger). 
V1VIP.\RI1).E. 
Vivipara lanfjtonensi^ (Hudlestoii), 
scoika (Tate). 
VALV.vnn.E. 
Valrafa comes Hndleston, 
priecnrsor Tate. 
NERITID/E. 
Aki'itina arata Tate, 
staffinensis Forbes. 
UNIONID.E. 
Unio distortiis Bean, 
staffincnsis Forbes. 
CORBICULID.E. 
Corbicida arata (Forbes), 
brj/cci (Tate), 
cucidlafa (Tate), 
vunninghami (Forbes), , 
jamesoni (Forl)es), 
maceullochi (Forbes). 
'I'he Middle Oolites embrace the Kelloway Rock, O.xford Clay, and 
Coral Rag, and exhibit no terrestrial or fluviatile fossil remains. 
The Upper Oolites include the Kimmeridge Clay, Portland Lime- 
stone, and the Piirbeck beds; the latter strata display a prevalence of 
freshwater conditions, the grey freshwater limestones so characteristic 
of this formation known as Purbeck marble, which was so largely used 
by mediccval architects for the interior ornamental parts of ecclesias- 
tical edifices, being almost entirely made np of fossilized Vivipara, the 
Vivipitra elungata being the predominant si)ecies. The deposits also 
show an increase in the Melaniidcv, while Physa makes its appear- 
ance. 
The land and freshwater fossils of this epoch embrace the following- 
species : — 
LIMN.Ein.E. 
Liinna fi ji/ii/suidcs Fibber, 
I'hi/sa bristovi Lyell, 
U'caldiana t'oqnaiid, 
Planorbis Jishcri Forbes. 
MKLANIID.E. 
Mclani(( jnipici (,J. de C. Sow.), 
Melanopsi.s at/cnnafa J. de C. Sow., 
liarpaformis Dunker, 
popei J. de C. Sow., 
riajosa Dunker, 
trkarinata J. de C. Sow. 
VAI.VATin.E. 
Valcata hclkoidcs Forbc.s. 
VIVIPARIDAS. 
Vivipara curinifcra (J. de C. Sow.). 
clongata (J. de C. Sow.), 
sussexicnsis (Maiitell). 
UNIONIDyE. 
Unio comprcssus J. de C. Sow., 
valdcnsis Mantell, 
A nodonta giurbcckensis Morris. 
CORBICULID.E. 
Corbicnln angulata (J. de C. Sow.), 
clongata (J. de C. Sow.), 
gibbosa (,J. de C. Sow.), 
media (.J. de C. Sow.), 
mcmbranacca (,J. de C. Sow.). 
The Cret.vceous (creta, chalk) system, which terminates the 
Mesozoic period, is named from the chalk which constitute its most 
characteristic strata, the freshwater deposits of the lower division 
are known as the Wealden, from their best development being in the 
Weald, the formation is considered to be probably derived from the 
accumulations, either in a lake or in an estuary of the detritus of a 
