i6 4 



OUR COMMON BRITISH FOSSILS. 



out into a trumpet-shaped mouth, frequently very 

 prettily marked. The holes of Arenicolites sparsus 

 and Arenicolites didymus are in pairs, and are found 

 in the same beds as Histioderma. 



Fig. 131. Tentaciilites anmilatus (a supposed Silurian Annelid with calcareous 



tube). 



The flag-stones obtained from the Millstone grit 

 formation in Lancashire and Yorkshire have their 

 surfaces frequently knobbed irregularly with the casts 

 of worm-furrows. Young geologists who often sigh 



