Ch. XVII.] MAESTEICHT BEDS. 237 



4. Upper greensand, occasionally "with beds of chert, and with chloritic marl 



(eraie chloritee of French authors) in the upper portion, 

 0. Gault, including the Blackdown beds, 



LOWER CRETACEOUS (or Neocomian). 



B, 1. Lower greensand — Greensand, Ironsand, clay, and occasional beds of lime- 

 stone (Kentisli Rag), 

 2. Wealden beds or Weald clay and Hastings sands,* 



Maestrickt Beds. — On the banks of the Meuse, at Maestricht, reposing 

 on ordinary white chalk with flints, we find an upper calcareous formation 

 about 100 feet thick, the fossils of which are, on the whole, very pecuhar, 

 and all distinct from tertiary species. Some few are of species common 

 to the inferior white chalk, among which may be mentioned Belemnites 

 Qnucronoius (fig. 256, p. 245) and Pecten quadricostaius, a shell i^- 

 garded by many as a mere variety of P. quinquecostatus (see fig, 271). 

 Besides the Belemnite there are other genera^ such as Baculite and Ha- 

 mite, never found in strata newer than the cretaceous, but frequently met 

 with in these Maestricht beds. On the other hand. Valuta, Fasciolaria, 

 and other genera of univalve shells, usually met with only in tertiary 

 strata, occur. 



The upper part of the rock, about 20 feet thick, as seen in St. Peter's 

 Mount, in the suburbs of Maestricht, abounds in corals and Bryozoa, often 

 detachable from the matrix ; and these beds are succeeded by a soft yel- 

 lowish limestone 50 feet thick, extensively quarried from time immemorial 

 for building. The stone below is whiter, and contains occasional nodules 

 of gray chert or chalcedony. 



M. Bosquet, with whom I examined this formation (August, 1850), 

 pointed out to me a layer of chalk from 2 to 4 inches thick, containing 

 green earth and numerous encrinital stems, which forms the line of de- 

 marcation between the strata containing the fossils peculiar to Maestricht 

 and the white chalk below. The latter is distinguished by regular layers 

 of black flint in nodules, and by several shells, such as Terehratula carnea 

 (see fig, 267), wholly wanting in beds higher than the green band. Some 

 of the organic remains, however, for which St. Peter's Mount is cele- 

 brated, occur both above and below that parting layer, and, among 

 others, the great marine reptile called Mosasaiirus (see fig. 247), a sau- 

 rian supposed to have been 24 feet in length, of which the entire skull 



* M. Alcide D'Orbigny, in his valuable work entitled Paleontologie Francaise, 

 has adopted new terms for the French subdivisions of the Cretaceous Series, which, 

 60 far as they can be made to tally with English equivalents, seem explicable thus . 



Etage Danien. Maestricht beds, 



Etage Senonien. White chalk, and chalk marl. 



Etage Turonien. Part of the chalk marl. 



Etage Cenomanien, Upper greensand, 



Etage Albien, Gault. 



Etage Aptien. Upper part of lower greensand. 



Etage Neocomien, Lower part of same. 



Etage Neocomien 



inferieur. Wealden beds and contemporaneous marine strata. 



