Ch. XXIII.] 
MAESTRICHT AND VfEALDEN BEDS. 
325 
the lower green-sand. The first of these groups is seen at 
St. Peter's Mount, Maestricht, reposing upon the upper flinty- 
chalk of England and France. It is characterized by a pecu- 
liar assemblage of organic remains, perfectly distinct from those 
of the tertiary period. M. Deshayes, after a careful compa- 
rison, and after making drawings of moi*e than 200 species of 
the Maestricht shells, has been unable to identify any one of 
them with the numerous tertiary fossils in his collection. On 
the other hand, there are several shells which are decidedly 
common to the calcareous beds of Maestricht and the white 
chalk. The names of twelve of these, communicated by M. 
Deshayes, will be found in Appendix II., p. 60. 
But the fossils of the Maestricht beds extend not merely 
into the white chalk of the French geologists, but into their 
' green-sand,' which appears to correspond very nearly with 
the upper green-sand of the English geologists. A list of 
five species of shells, common to the Maestricht beds and 
the upper green-sand of France, will be found in Appendix 
II., p. 60. 
It will be seen by the above lists, that the belemnite, one of 
the cephalopodes not found in any tertiary formation, occurs 
in the Maestricht beds; an ammonite has also been discovered 
in this group by Dr. Fitton, and is now in the collection of the 
Geological Society of London. 
That gigantic species of reptile, the Mososaurus of Maestricht, 
has also been found by Mr. Mantell in the English chalk. 
2. The Wealden, or the strata from the Weald clay to the 
Purbeck limestone inclusive. 
The numerous fossil-shells of this group are referrible to fresh- 
water genera, which are associated with many remains of 
fluviatile and terrestrial reptiles and land-plants. We believe 
that no species, whether animal or vegetable, in this group, has 
been distinctly identified with any found either in the super- 
incumbent marine beds of the first division, or in the subjacent 
rocks of the group No. 3, which are also of marine prigin. 
