FOSSIL WORMS, 173 



stone of the Gault of Kent is frequently full of annelid 

 borings. A hard band of clay in the Gault at Folke- 

 stone, and near Charing, in the same county, is 

 occupied with serpula tubes, which form a thin stratum 

 two inches thick. Serpula plexus is always common 

 in the Chalk ; and near Norwich and Margate it 

 frequently occurs in masses, or completely investing 

 the larger fossil shells, such as Inoceramus. 



In the Eocene beds the commonest fossil worm- 

 tubes are those of Ditriipa^ which was evidently free 

 or unattached to objects, after the manner of the 

 TentaculiteSy etc., already described. It is usually 

 found in large numbers, and appears to have been 

 gregarious in its habits. We may get a large quantity 

 of this fossil worm in the London Clay beds of 

 Bognor, Hampshire. Ditrupa plaiia is the name 

 of the common species. Ditrupa is also found in 

 the crag beds of Suffolk, where it may have been 

 redeposited there from denuded Eocene strata, 



