Ch. XXIII.] MAESTRICIIT AND V,'EALDEN 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 more 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, theMososaurus 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 origin. 



