356 SPECIAL GEOLOGY. 



The marine deposits of the valley of the Clyde, near 

 Glasgow, which contain from 85-90 per cent, of existing 

 species, represent the newer pliocene ; whilst the crag 

 of Norfolk is regarded as older pliocene, the red and 

 coralline crag of Suffolk is referred to the miocene group. 



FIG. 254. Trophon elegans, ventral side, from the red crag. 



The stratigraphical order of the crag was determined by 

 Mr. Charlesworth,* to be : 



1. The mammaliferous or Norwich crag. 



2. The red crag. 



3. The coralline crag. 



The mammaliferom crag consists of shelly beds of sand, 



* In a paper read to the British Association, in 1836. 



