inocerata"--'American Journ. of
Science and Arts,' vol. xi. Marsh.
(45) 'Principal Characters of the Brontotheridae' (Ibid.) Marsh.
(46) 'Principal Characters of the Tillodontia' (Ibid.) Marsh.
(47) "Extinct Vertebrata of the Eocene of Wyoming"--'Geological
Survey of Montana,' &c., 1872. Cope.
(48) "Ancient Fauna of Nebraska"--'Smithsonian Contributions to
Knowledge,' vol. vi. Leidy.
(49) 'Manual of Geology.' Dana.
(50) "Palaeontology and Evolution" (Presidential Address to the
Geological Society of London, 1870)--'Quart. Journ. Geol.
Soc.,' vol. xxvi. Huxley.'
(51) 'Mineral Conchology.' Sowerby.
(52) 'Description des Coquilles Fossiles,' &c. Deshayes.
(53) 'Description des Coquilles Tertiaires de Belgique.' Nyst.
(54) 'Fossilen Polypen des Wiener Tertiaer-beckens.' Reuss.
(55) 'Palaeontologische Studien ueber die aelteren Tertiaer-schichten
der Alpen.' Reuss.
(56) 'Land und Suess-wasser Conchylien der Vorwelt.' Sandberger.
(57) 'Flora Tertiaria Helvetica.' Heer.
(58) 'Flora Fossilis Arctica.' Heer.
(59) 'Recherches sur le Climat et la Vegetation du Pays
Tertiaire.' Heer.
(60) 'Fossil Flora of Great Britain.' Lindley and Hutton.
(61) 'Fossil Fruits and Seeds of the London Clay.' Bowerbank.
(62) "Tertiary Leaf-beds of the Isle of Mull"--'Quart. Journ.
Geol. Soc.,' vol. vii. Edward Forbes.
(63) 'The Geology of England and Wales.' Horace B. Woodward.[25]

[Footnote 25: This work--published whilst these sheets were going
through the press--gives to the student a detailed view of all the
strata of England and Wales, with their various sub-divisions,
from the base of the Palaeozoic to the top of the Tertiary.]

CHAPTER XXI.

THE QUATERNARY PERIOD.

THE POST-PLIOCENE PERIOD.

Later than any of the Tertiary formations are various detached
and more or less superficial accumulations, which are generally
spoken of as the _Post-Tertiary formations_, in accordance with
the nomenclature of Sir Charles Lyell--or as the _Quaternary
formations_, in accordance with the general usage of Continental
geologists. In all these formations we meet with no _Mollusca_
except such as are now alive--with the partial and very limited
exception of some of the oldest deposits of this period, in which
a few of the shells occasionally belong to species not known
to be in existence at the present day. Whilst the _Shell-fish_
of the Quaternary deposits are, generally speaking, identical
with exis