FOSSIL MOLLUSC A. 279 



be the fossil faeces of animals, whence their name) 

 are worked. More than two million pounds' worth 

 of these " coprolites " have been excavated and con- 

 verted into artificial manures since the late Professor 

 Henslow found out what they were, nearly forty years 

 ago. The " coprolites " are richest at the base of the 

 shell-crags, where they form part of a bed in which 

 we get the remains of mastodon, tapir, hipparion, 

 rhinoceros, deer, etc. ; also roundish and elongated 



Fig. 265. Emarginulai fissura : a, natural size ; b, magnified ; c, lower side 

 (Crag and recent). 



masses of coffee-coloured sandstones, which the visitor 

 will find lying in heaps near every coprolite pit. 



Very singular are these roundish masses of sand- 

 stone, most of which are about the size of one's fist. 

 From Foxhall, the bed containing them (which 

 usually lies directly on the London clay) extends to 

 Felixstowe, and heaps of them may be seen by the 

 roadside, waiting to be broken up for road-mending. 

 They are very curious, for they represent a lost 

 geological formation, older than the Coralline Crag 

 (for they are also found under the latter), which is 

 probably of late Miocene age. The rounded speci- 



