50 



OUTLINES OF GEOLOGY* 



position the legs of a lizard, with vertebrae similar to those of 

 a fish. 



(3.) The Plesiosaurus, having a body shaped like that of 

 the tortoise. To this body is adapted a neck like that of 

 the swan, which contains a greater number of vertebra? than 

 that of any other animal, either extinct or living. 



(4.) The Iguanodon, so called because its teeth have the 

 same structure as those of the living genus Iguana. 



(5.) The Pterodactylus, a saurian, in which the limbs 

 were made to move wings, exactly as those of the existing 

 genus of bat ; exhibiting the remarkable fact of an adapta- 

 tion to a similar mode of life, in animals situated almost at 

 the extreme of the grand division of vertebratse. 



114. A few mineral veins are found in this group, which 

 is the highest in which they make their appearance ; they 

 do not, however, contain any of the useful metals. Hydrated 

 oxide of iron, manganese, and pyrites are found in the joints 

 of the strata. 



115, The strata of the oolitic group are, with the exception 

 of t hose of the lias, conformable with each other, but uncon- 

 formable with the chalk. The lias appears not only to have 

 been deposited, but to have been much disturbed, before the 

 lower oolite began to be deposited. In some instances, horizon- 

 tal strata of oolite are found resting on the edges of strata of 

 lias, inclined at an angle of 45°. The extent of the lias also ap- 

 pears to be much greater than that of the oolites. For these 

 reasons, Brogniart classes the lias with the succeeding group. 



The true oolites pass into freestones, which contain sand 

 disseminated through them. These furnish some of the most 

 valuable building stones. Some of these have the invaluable 

 property of being soft when taken from the quarry, and 

 hardening when exposed to the air. Among these may be 

 mentioned the Portland and Bath freestones. 



Fullers' earth occurs in regular beds, in the lower oolitic 

 series. 



