SIXTH GEOLOGICAL EPOCH. 



LESSON IV. 



- 



SECONDARY FORMATION Continued. 



SIXTH GEOLOGICAL EPOCH. Creta'ceous Formation Lower Cre- 

 ta'ceous System Fossils Wealden Deposit Greensand 

 Gault Fossils Upper Creta'ceous System Fossils Extent 

 of Creta'ceous Formation Table of Formations. 



SIXTH GEOLOGICAL EPOCH. 



CRETA'CEOUS FORMATION. 

 (Secondary Formation Continued.] 



1. Next in order above the Jura'ssic system we find, in discord- 

 ant stratification, immense Creta'ceous deposits in a great many lo- 

 calities ; these deposits may be divided into several others, accord- 

 ing to the discordance of stratification observed in some of their 

 divisions. The cretaceous formation (from the Latin, creta, chalk) 

 may be divided into the upper and lower chalk. 



2. The LOWER, or INFERIOR CRETA'CEOUS system : Neocomian 

 of the French ; the Shanklin, or Lower Green Sand of the Eng- 

 lish. The first deposits formed above the o'olite are composed of 

 marls, then a yellowish limestone, characterized by great numbers 

 of genus Spata'ngus (fig. 114), with a multitude of the remains 

 of shells and polypa'ria of different genera. This limestone is 

 sometimes in continuous layers of considerable thickness, some- 



-. \U.~Spatangus Fig. 1 15. Exo'gy'ra Fig. 116. Lima 

 retusus. subplica'ta. elegans. 



1 What is found next above the Jurassic formation ? Why is it termed 

 Creta'ceous ? How is the creta'ceous group divided ? 



2. How are the first deposits above the o'olite characterized? What is 

 .umachella ' What is found next above the yellow limestone ? 



