250 



PA.LJEONTOLOGY. 



THE following Table, by Alcide D'Orbigny,* exhibits a stratigraphical distri- 

 bution of the EIGHTEEN THOUSAND SPECIES of MOLLUSCA and RADIATA, 

 which served as the basis of his generalisations on the speciality of Fossil 

 Animals. It enables the student to form a correct idea of the numerical 

 value of the species which characterise each stage and period into which the 

 fossiliferous rocks are divided. 



* Cours de Paleontologie, p. 260. The English equivalents of D'Orbigny's 

 stages have been introduced to assist the student. 



