100 VERMES. 



which do not live in tubes, are provided with minute 

 chitinous jaws, and in some formations, especially the 

 Ordovician and Silurian, these are abundantly preserved. 



Serpula. Tube calcareous, long, round, angular or 

 flattened; straight, curved irregularly, or sometimes spiral, 

 closed at one end; generally 'attached to some foreign 

 object by a portion of its surface. Carboniferous to present 

 day. 



Spirorbis. Tube calcareous, small, spiral, attached 

 by one side. The spiral either left-handed or right- 

 handed, the last whorl often produced into a free tube. 

 Ordovician to the present day. 



Distribution of the Vermes. 



Practically all the worms found fossil belong to the 

 Polychseta, the earliest examples occurring in the Cam- 

 brian beds. In addition to the worm-tubes and jaws, we 

 find in the rocks numerous trails and burrows which are 

 regarded as having been formed by worms, but it is 

 impossible to speak definitely of the affinities of these 

 forms. And in many cases it is quite probable that the 

 tracks may have been made by other animals such as 

 crustaceans and gasteropods. 



