Geology of England and Wales, '^'' 8fc. 219 



characteristic ; consisting of bones of the Ichthyosaurus 

 and numerous shells. 



Lower Dimsion of Oolites. 



This division far exceeds the two preceding; in thickness 

 and importance. The subdivisions, which might with 

 propriety be made in it, are so numerous, that the writers 

 very wisely refer the whole to two sections, viz. its upper 

 and lower beds : all the upper beds being subordinate to 

 the great oolite ; and the lower, to the calcareo-siliceous 

 sind, which fortns their base. Viewed generally, both 

 these series of beds consist of one vast oolitic mass, resting 

 upon calcareo-siliceous sand. These oolitic beds, howev- 

 er, embrace several varieties, characterized principally by 

 being more or less argillaceous. These are denominated, 

 in a descending order, Comhrash, Stonesfeld Slate, Forest 

 Marble, and Great Oolite. The inferior members of the 

 third, or lower system of Oolites, are the fuUer^s Earth. In- 

 ferior Oolite Sand, and Marlstone. The inferior is distin- 

 guished from the Great Oolite, by the larger proportion of 

 brown oxide of iron, that is disseminated through its mass. 

 The sand and sandstone are slightly calcareous, highly 

 ferruginous, and frequently micaceous; containing but ievv 

 fossils The marlstone is sandy, gritty, micaceous, and 

 of a green color ; presenting but few organized Vemains. 



The lower division of the oolitic series, however, is pe- 

 culiarly interesting for the richness and variety of its fos- 

 sils. The testacea are very abimdant : and a more com- 

 plete and extensive list of these is given in the work before 

 us. than of any other formation. Echinites, encrinites, 

 corralloides, madrepores, tubipores, millepores, and alcyo- 

 nia are also found. But the Stonesfield slate, which is 

 with great probability referred to the Oolitic series, is most 

 remarkable for its petrifactions. Here occurs a species of 

 Didelphys, one of the Opossum tribe; an immense animal, 

 resembling the Monitor, 40 feet long and 12 feet high ; two 

 or three species of tortoise; teeth, palates, and vertabrae of 

 fishes; leg and thigh bones of birds ; two or three species 

 of Coleopterous insects ; two or three varieties of the crab, 

 ©r lobster; and ferns, flags, and mosses. This remarkable 



