'Supplement to the Corals of the Oolitic Formation'
(Palaeontographical Society). Martin Duncan.
(21) 'Monograph of the Belemnitidae' (Palaeontographical Society).
Phillips.
(22) 'Structure of the Belemnitidae' (Mem. Geol. Survey). Huxley.
(23) 'Sur les Belemnites.' Blainville.
(24) 'Cephalopoden.' Quenstedt.
(25) 'Mineral Conchology.' Sowerby.
(26) 'Jurassic Cephalopoda' (Palaeontologica Indica). Waagen.
(27) 'Manual of the Mollusca.' Woodward.
(28) 'Petrefaktenkunde.' Schlotheim.
(29) 'Bridgewater Treatise.' Buckland.
(30) 'Versteinerungen des Oolithengebirges.' Roemer.
(31) 'Catalogue of British Fossils.' Morris.
(32) 'Catalogue of Fossils in the Museum of Practical Geology.'
Etheridge.
(33) 'Beitraege zur Petrefaktenkunde.' Muenster.
(34) 'Petrefacta Germaniae.' Goldfuss.
(35) 'Lethaea Rossica.' Eichwald.
(36) 'Fossil Fishes' (Decades of the Geol. Survey). Sir Philip Egerton.
(37) 'Manual of Palaeontology.' Owen.
(38) 'British Fossil Mammals and Birds.' Owen.
(39) 'Monographs of the Fossil Reptiles of the Oolitic Formation'
(Palaeontographical Society). Owen.
(40) 'Fossil Mammals of the Mesozoic Formations' (Palaeontographical
Society). Owen.
(41) 'Catalogue of Ornithosauria.' Seeley.
(42) "Classification of the Deinosauria"--'Quart. Journ. Geol. Soc.,'
vol. xxvi., 1870. Huxley.

CHAPTER XVII.

THE CRETACEOUS PERIOD.

The next series of rocks in ascending order is the great and
important series of the Cretaceous Rocks, so called from the
general occurrence in the system of chalk (Lat. _creta_, chalk).
As developed in Britain and Europe generally, the following leading
subdivisions may be recognised in the Cretaceous series:--

1. Wealden, \_ Lower Cretaceous.
2. Lower Greensand or Neocomian, /
3. Gault, \
4. Upper Greensand, |_ Upper Cretaceous.
5. Chalk, |
6. Maestricht beds, /

I. _Wealden_.--The _Wealden_ formation, though of considerable
importance, is a local group, and is confined to the southeast
of England, France, and some other parts of Europe. Its name is
derived from the _Weald_, a district comprising parts of Surrey,
Sussex, and Kent, where it is largely developed. Its lower portion,
for a thickness of from 500 to 1000 feet, is arenaceous, and is
known as the Hastings Sands. Its Upper portion, for a thickness
of 150 to nearly 300 feet, is chi