MOSASAURIAN PERIOD. 181 



Annulosa. Enaliosauria. 



Fishes. Crocodilia. 



Dinosauria. 



Freshwater remains of plants occur in the carbonaceous sand- 

 stones and shales, with Unionidse, and many land plants, espe- 

 cially Ferns, Cycadacese, Lycopodiacese, and Equiseta. 



After the completion of probably the whole oolitic series of 

 rocks, the downward movement to which in these regions the 

 sea-bed was subject, was interrupted, at least locally, by a remark- 

 able elevation. The effect of this is conspicuous on the line of 

 the Wolds where the strata of the oolitic series are bent into a 

 broad anticlinal, of which the axis passes near Bishop Wilton, 

 probably in a direction from west to east. The oolitic and lias 

 strata dipping from this axis on one side to the north, and on 

 the other to the south (but very moderately), are, as in the cases 

 already given, the Silurians and the coal-measures, wasted 

 and worn down to a surface nearly horizontal on the great scale, 

 on which the chalk rests unconformably, just as the mountain 

 limestone rests on the Silurians, and the magnesian limestone 

 on the coal. At Bishop Wilton the removal of the oolite and 

 lias is so nearly complete, that only a small thickness of lias 

 separates the chalk from the new red marls. At Huggate also, 

 within the area of the Wolds, lias was found immediately below 

 the chalk. 



There is no sufficient evidence to show whether this elevation 

 was occasioned by gradual or sudden application of power. The 

 level of the wasted surface of the oolites and lias below the 

 chalk of the Wolds is about 1000 feet below that of the highest 

 points of the North York Moors. If, according to the now 

 generally received opinions in geology, we admit that the waste 

 of the surface referred to was accomplished at a small depth 

 under the sea, these lands, not in their present form indeed, may 

 have been, and probably they were at that epoch, above the level 

 of the sea. 



MOSASAURIAN PERIOD. The depression of the sea-bed con- 



