FOSSIL WORMS. 



163 



Let us take the wandering worms (Errantia) first 

 in order, as they probably were first in point of 

 appearance in the earlier seas of our globe. The names 

 assigned to the com- 

 monest of the tracks and 

 trails believed to have 

 been left by them are 

 borrowed in most in- 

 stances from modern 

 genera ; thus we have 

 Phyllodocites, Myrianites, 

 Crossopodia, A renicolites, 

 etc. The markings we 

 have to explain are of 

 two kinds, burrows and 

 trails. The sea-worms 

 making the former were 

 doubtless of similar 

 habits to our common 

 lob-worm {A renicolapis- 

 catorum} and the generic 

 name of Arenicolites at 

 once indicates this. 



The Cambrian rocks of Bray Head, near Dublin, 

 have long been famous for the occurrence of markings 

 left by an ancient burrowing worm, named by Dr. 

 Kinahan Histioderma Hibernicum, associated with 

 the zoophyte Oldkamia. The tubular casts of these 

 worm-holes may be obtained. The upper part swells 



Fig. 130. Coriaceous tube of Sabella 

 unispira (recent). 



