MESOZOIC TIME — CRETACEOUS. 859 



ordinarily black or grayish-black flint, is sometimes chalcedony or agate, and 

 on the other hand, it is often white exteriorly from admixture with chalk. 

 The fantastic shapes of some flints are often due in part to the fossils 

 they include. 



The rocks in northern France or Belgium much resemble those of England. 

 In Germany, above the Lower Cretaceous, there is a large predominance of 

 sandstones and marls. In Switzerland, the Lower Cretaceous of the Jura, 

 about ISTeufchatel, is mostly limestone ; and of the same nature is the chief 

 part of the Upper in other parts of Switzerland and the Austrian Alps. The 

 same is true for most of the Cretaceous of Italy, northern Africa, Syria, the 

 Mediterranean region being marked in places by coral reefs, Hippurite lime- 

 stone, and other evidences of pure ocean waters. 



The following are the subdivisions adopted in France and Belgium and Switzerland. 

 (See further on their distinctions, page 864.) 



2. Upper Cretaceous. 



4. Danian. — 1. Maestrichtian or Dordonian ; 2. Garumnian (Pisolitic limestone). 



3. Senonian. — 1. Santonian ; 2. Campanian. 



2. TtJRONiAN. — 1. Ligerian ; 2. Angoumian. 



1. Cenomanian. — 1. Rhotomagian ; 2. Carentonian. 



1. Lower Cretaceous. 



4. Albian (= Gault). — Vraconnian = Upper Albian, at Cheville in the Valais. 



3. Aptian (= rest of Lower Greensand). 



2. Urgonian (= lower part of Lower Greensand). — 1. Urgonian ; 2. Rhodanian. 



1. Neocomian (= Wealden). — L Valenginian (= Hastings sand); 2. Hauterivian 

 ("Weald clay) . 



LIFE. 



Plants. — The plants of the Wealden, and the rest of the Neocomian in 

 England and Europe, are Cycads, Eerns, and Conifers, as in the Jurassic, with 

 a show of progress in the first appearance of species of the genera Pinus and 

 Abies, the true Pines and Spruces, but with no Angiosperms. But in the Gault 

 and the Upper Cretaceous occur leaves of Angiosperms of many common 

 kinds, though all of extinct species ; as the Magnolia, Myrtle, Willow, Wal- 

 nut, Maple, Pig, Holly, besides a Redwood (Sequoia) ; and there were also 

 Palms, of the genus Palmacites. No remains of Lower Cretaceous Angio- 

 sperms and Palms have been reported from England. Vegetable remains 

 are rare fossils because the beds are mostly marine. 



The microscopic Protophytes, called Diatoms and Desmids, are found in 

 some of the beds, especially in the flint. The Desmids are far the more 

 common because not siliceous, and therefore not dissolved ; the kinds called 

 Xanthidia are especially abundant, and are similar to those from Devonian 

 hornstone (page 583). Coccoliths are common in the Chalk. 



