2lr8 Review of " Outlines of the 



Upper division of the Oolitic Series, 



The first subdivision of this series is the Purbeck beds. 

 From these beds is obtained the Purbecic Marble, and they 

 consist of thin strata of argillaceous limestone, alternating 

 with schistose marbles. This rock contains subordinate 

 beds of workable gypsum and numerous shells ; some of 

 which are said to be fresh water shells: also beautiful im- 

 pressions offish, and the head of a crocodile. 



The Portland Oolite, the next member of the upper 

 oolitic system, consists of several beds of coarse, earthy 

 limestone. It is quarried extensively and constitutes most 

 of the building stone in the vicinity of London. The or- 

 ganic remains are fish, shells, and wood. 



The third member is the Kimmeridge Clay, being com- 

 posed of a blue slaty, or greyish yel'.ow clay, which con- 

 tains selenite, and sometimes beds of highly bituminous 

 shale Extinct genera, allied to the order Lacerta, are 

 among the fossils of this clay ; and also a species of Ich- 

 thyosaurus, a variety of Plesiosaurus ? bones, apparently of 

 cetacea, and numerous shells. 



Middle Division of Oolites, 



The Coral Rag occurs first in this division. It compris- 

 es a series of beds from 100 to 200 feet thick ; the calcare- 

 ous matter prevailing in the upper part, and the siliceous 

 in the lower. The upper beds are a calcareous freestone, 

 full of comminuted shells : the middle part is a loose, rub- 

 bly limestone, almost entirely made up of a congeries of 

 several species of madrepores ; and the lower beds are a 

 thick deposite of yellow colored, quartzose sand, usually 

 containing about one third of calcareous matter, and 

 abounding in fossils. This is the newest rock in England, 

 in which madrepores occur in any considerable variety, or 

 quantity. 



The Oxford clay, the second member of this division, 

 forms beds of a tenacious and adhesive clay, of a dark blue 

 color, of immense thickness : the lower part occasionally 

 containing irregular beds of limestone. "Iron pyrites and 

 selenite occur abundantly in this as indeed in all argillace- 

 ous formations." The organic remains are peculiar and 



