1866.] 



DAWSON LAUEENTIAN ANNELIDS. 



609 



rock, and lined around their circumference with dense and dark- 

 coloured siliceous matter, while the axis, which is often of a bilohate 

 form, is comparatively transparent and of softer texture. The per- 

 forations are often at right angles to the bedding, hut in some cases 

 nearly parallel with it. 



In regard to the origin of these perforations, I suppose that they 

 may have been either (1) burrows of worms filled with sand sub- 

 sequently hardened and stained at the surface, or (2) tubes com- 

 posed of sand, like those of Sahella, or (3) cavities left by the 

 decay of Algae, and filled with sand. The first I think the most 

 probable view. 



Figs. 1-5. — Illustrating supposed Annelid-tuhes from tlie 

 Laurentian Rocks of Canada. 



'4 







b e a 



Fig. 1. Transverse section of Worm -burrow. Magnified, as a transparent object. 



a. Calcareo-siliceous rock. | c. Sand agglutinated and stained black. 



h. Space filled with calcareous spar. I d. Sand less agglutinated and unco- 



I loured. 



Fig. 2. Transverse section of Worm-burrow on weathered surface. Natural size. 



3. The same, magnified. 



4. Spicule, magnified. 



5. Lenticular body, magnified. 



I may add that the beds at Madoc containing these supposed 

 fossils, hold also on their weathered surfaces impressions with rude 

 casts of concentric laminae, like those of Stromatopora or Eozoon, 

 but too obscure for determination. The limestones interstratified 

 with these beds also contain fragments of Eozoon, not fossilized by 

 serpentine, but simply by carbonate of lime, carbonaceous fibres, 

 spicules like those of sponges, and lenticular bodies of unknown 

 nature. 



