38 
The tracks of worms are numerous. No doubt 
these worms drew together a concourse of birds to the 
shores on which they rolled. On various slabs we 
find long cylindrical furrows, about the eighth of an 
inch in diameter, and of different lengths; one of 
them, in the slab from Dr. Deane, bemg eight or nine 
inches long. ‘To these impressions the name of Hmr- 
pysTezouM, from éprori-, crawling, has been given. 
They vary, however, and some of them are very likely — 
to be the tracks of the common earth-worm, or of 
some species of worm which existed when these rocks 
were formed. ‘These impressions vary in length and 
in diameter; some of them are moderately regular, 
and others irregularly curved. 
Very interesting tracks have been found in the 
ancient Potsdam white sandstone of Beauharnais, on 
the St. Lawrence, by Mr. Logan, an excellent geolo- 
gist of Canada, and determined by Professor Owen to 
belong to Crustacea, crabs. ‘The number of impres- 
sions made by each foot is sometimes seven, sometimes 
eight, and even more. This track, showing the traces 
of Crustacea, goes to form another link in the chain of 
fossil footsteps. 
The Medusee, commonly called jelly-fish, dissolving 
