612 



SIR J. W. DAWSON ON BURROWS AND TRICKS OF 



covered with a bed of sand, hardened afterwards into rock. The 

 effect would be that, on weathering, all the prominent parts filled 

 with mud would disappear, leaving the slab in its present state. 



Pig. 15. — Worm-hurrows seen in section, owing to the manner of 

 preservation and weathering. Calciferous Sandstone ; St. Anne's. 

 (From a Photograph.) 



All of these tracks or burrows are of the plain cylindrical forms to 

 which the terms Flanolites, Nicholson *, and Arenicolites, Salter f, 

 have been applied, and which differ from Scolithus only in their 

 more tortuous character, and in their usually being casts of mere 

 trails on the surfaces of beds, rather than burrows or tubes pene- 

 trating them. I cannot doubt the origin of these markings, if for 

 no other reason, on account of their covering such great surfaces of 

 strata in a uniform manner. 



* ' Proceed. Roy. Soc' vol. xxi. 1873, p. 289 ; ' Manual Palaeont.' edit. 2 

 vol. i. p. 320. 



t ' Quart. Journ. Geol. Soc' vol. xiii. 1857, p. 204.. 



