i64 OUR COMMON BRJTJSH FOSSILS, 



out into a trumpet-shaped mouth, frequently very 

 prettily marked. The holes of Arenicoliies sparsiis 

 and Arenicoliies didyrmis are in pairs, and are found 

 in the same beds as Histioderma. 



Fig. 131. — TentaciiUtes annulatus (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 



