FOSSIL WORMS. 



165 



for opportunities to geologize abroad should keep 

 their eyes open to the periodical mending of the roads 

 and causeways of the towns in which they live. In 

 the neighbourhood of Manchester and Sheffield the 



Fig. 132. Tracks and Burrows of Arenicolites sparsus, with Oldhamiet. 



newly laid flags are often seen ripple-marked, and 

 worm-tracked or worm-burrowed. The Cambrian and 

 Silurian sandstones afford 

 similar evidence of shallow 

 water deposition. In the 

 Stiper Stones (Upper Cam- 

 brian) both casts and 

 burrows are abundant. In 

 the Bangor slate quarries 

 the markings are called 

 CkondriteS) from the origi- 

 nal belief that they were 

 impressions left by seaweeds, but I favour the 

 theory of their annelid origin. In the slate quarries 



Fig. 133. Burrows of Arenicolitet 

 didymits. 



