286 
ELEMENTS OF GEOLOGY. 
Fig. 229. 
six of Fusiis^ two of Trochus^ one of Patella., one of 
Fmargmula., etc.; on the whole, more than thirty univalves, 
spiral or patelliform. At the same time, some of the accom¬ 
panying bivalve shells, echinoderms, 
and zoophytes, are specifically identi¬ 
cal with fossils of the true Cretaceous 
series. Among the cephalopoda of 
Faxoe may be mentioned Baculites 
Faujasii (Fig. 229), and Belemnitella 
miicronata (Fig. 226, p. 283), shells of 
the white chalk. The Nautilus J)ani- Portion of BacuUtes FaujasU. 
CUS (see Fig. 230) is characteristic of Maestricht ainl Faxoe beds 
this formation ; and it also occurs in 
France in the calcaire pisolitique of Laversin (Department of 
Oise). The claws and 
entire skull of a small 
crab, Brachyurus ru- 
gosus (Schlott.), are 
scattered through the 
Faxoe stone, remind¬ 
ing us of similar crus- 
taceans inclosed in the 
rocks of modern coral 
reefs. Some small por¬ 
tions of this coralline 
formation consist of 
white earthy chalk. 
Composition, Extent, 
and Origin of the White Chalk. —The highest beds of chalk 
in England and France consist of a pure, white, calcareous 
mass, usually too soft for a building-stone, but sometimes 
passing into a more solid state. It consists, almost purely, 
of carbonate of lime; the stratification is often obscure, ex¬ 
cept where rendered distinct by interstratified layers of flint, 
a few inches thick, occasionally in continuous beds, but often- 
er in nodules, and recurring at intervals generally from two 
to four feet distant from each other. This upper chalk is 
usually succeeded, in the descending order, by a great mass 
of white chalk without flints, below which comes the chalk 
marl, in which there is a slight admixture of argillaceous 
matter. The united thickness of the three divisions in the 
south of England equals, in some places, 1000 feet. The sec¬ 
tion on the opposite page will show the manner in which the 
white chalk extends from England into France, covered by 
the tertiary strata described in former chapters, and reposing 
on lower cretaceous beds. 
Fig. 230. 
Nautilus Danicus^ Schl. Faxoe, Denmark. 
