ISO OUR COMMON BRITISH FOSSILS. 



buried themselves in the chalky mud of the ancient 

 sea in a similar manner. Some of the modern Echini, 

 on the other hand, have the power of hollowing for 

 themselves holes in the rocks by the sea, especially in 



Fig. 122. Ananchytes ovata, or "fairy loaf," a common Cretaceous Echinoderm: 

 a, base, showing position of mouth and anus. 



limestone rocks, which are not unfrequently found 

 riddled by them, just as they are by Pholas and other 



Fig. 123. Natural flint cast of interior of AnancJiyte (very common in Norfolk and 

 Suffolk), showing the perforations (in relief) for ambulacral or sucking-feet. 



boring molluscs. A pretty little sea-urchin, not quite 

 so big as a threepenny piece, which we find not 

 uncommonly fossilized in the Red Crag beds, is the 



