POST-TERTIARY FOSSILS. 
415 
The Pleistocene (wXeuTTos, most; Kau-ds, recent) Post Pliocene, 
Glacial, or Diluvial beds, as they are variously called, are rather few 
and fragmentary in this country, consisting only of such remnants as 
have escaped destruction by the enormous denudation to which its 
deposits have been subjected. 
The pleistocene beds would appear to have been deposited during 
a gradual refrigeration of the climate, until what is known as the 
“Ice Age” prevailed, the condition of a great part of the British Isles 
being compared at this period to that of Greenland at the present day. 
These deposits, also known as the Palieolithic age, are the first con- 
taining undoubted evidence of the existence of man, his presence at 
this period being attested by the discovery of the roughly chipped 
flint arrow-heads and other weapons and implements associated with 
remains of the mammoth, hippopotamus, rhinoceros, lions, bears, and 
other animals characteristic of the period in this country. 
The Holocene (oXws, entirely ; /catvos, recent) or Post Glacial period, 
is composed of recent superficial deposits, river alluvia, peat moors, 
sand dunes, lacustrine deposits, etc., which contain no fossilized 
remains of species now extinct, the differences shown by the mollusca, 
compared with those existing at the present day in the same region, 
being now confined to variations, which although they may not now live 
in the British Isles, yet are still found in neighbouring countries. 
It is also known as the Xeolithic age, the stone implements of the 
savage races of mankind living at this period being more highly 
finished than the ruder ones of the preglacial peoples. 
The Post-Tertiary fossils now extinct in this country are : 
LIMACID.E. 
Limax modioliformis Sandberger, 
HELICID.E. 
Helix friificinn Miiller, 
nemoralis v. creticola Alorch, 
rudcrata Studer, 
iimbrom Paitscli, 
PUPID.E. 
Vertigo concinna Seott, 
Claiisilia piimila v. sejunctn Scliiiiidt, 
LIMX.EIU.E. 
Lirnmea pedustris aff. diluviana And. 
VIVIPARID.E. 
Vivipara clactonensis (S.V. Wood) 
PALUDESTRINID.E. 
Paludestrina marginata (Alicliaud), 
Bithgnella sfeeni (E. von Marten.s), 
Bithgnia ovatida Sandberger, 
Neinatiirclla runtoniuna Sandberger, 
UXIO.MD.E. 
Unio Uttorcdis Lamarck. 
pictorum V. limosa Nils. 
copancuLiD.E. 
Spluerium corneinn v. vicenamim Koh. 
Corbicida flumimdis (Miiller), 
Pisidium amnicuni v. astartoides 
(Sandberger). 
The faunal changes which have taken place on the earth is shown 
by the preceding varying lists of the species obtained from the different 
geological formations. These changes in the molluscan fauna have 
their analogies or counterparts in the succession of life observed in all 
