TERRESTRIAL AND FRESHWATER ANIMALS. 185 
PLATE X. 
Figs. 1 & 2. Plumes left by ice-crystals. 
Fig. 3. Track of burrowing animal, showing how it sometimes crosses and 
sometimes again enters the old track. 
4, Wriggling track of small worms. Track of animal with feet, showing 
how it draws its legs closer to the body in one part than in another, 
thus producing a tapering mark. ‘Track of larva, in which the 
cross-bars due to the impress of the body-rings are clearly shown. 
Spiral track, with the hole in the centre by which the animal came 
up to the surface. 
Puate XI. 
Fig. 1. Track of small burrowing animal (beetle ?), showing the manner 
in which it at first looks out from its tunnel at regular intervals, 
occasionally leaving it for a short distance, and then goes away un- 
interruptedly under the surface. 
2. The same, showing in places the track of the same animal when not 
burrowing. The footmarks are sometimes fairly distinct, but 
sometimes only a confused brushing of the surface. 
3. Track of Water-beetle, showing an approach to the quadrilobate form. 
4, Track of worm, feeling its way out in various directions from the end 
of a tunnel which it has formed just under the surface of the mud. 
In this the bars formed by the bristly rings of the worm are not 
obliterated by the posterior portion of the animal’s body being 
subsequently dragged over them. 
5, Footmark of frog, in relief on the upper surface of slab. 
6. Bubble-rings. 
7. Rain-spots. 
DIscUSSION. 
Prof. Dawson remarked that in the Silurian, Devonian, and Car-: 
boniferous rocks of Canada were forms described as fucoids which 
he himself thought were more probably traces of animals, though it 
was hard to say of what animals. The deposition of sediment from 
coarse to fine, described by the author, might be seen in the Bay of 
Fundy. Shrinkage-cracks had often been described as fucoids, one 
of them being a cracked surface, modified by the in-running of little 
rills of water. So, too, had the marks made by rills on the mud. 
It was well to remember that dissimilar animals might make similar 
tracks, and similar animals, under different circumstances, would 
make dissimilar tracks. Limulus, for instance, made three kinds of 
tracks. The explanation of the bilobate worm-marks given by 
the author appeared to him to be correct; also that of the tracks 
in relief on the upper surface. ‘The pulling-up of the mud might 
often be seen in modern tracks. Nearly all these phenomena 
could be paralleled by the action of sea-worms, Crustacea, &c., on 
the sea-bottom. We must, however, remember that in some cases 
structure remained, showing that in these we had vegetable tissues. 
Prof. T. Rupert Jonus said that there were some drawings of 
markings by marine animals by the late Hugh Strickland in the 
possession of the Society. He also described various markings of 
characters other than those described by the author. He thought 
that the Crustacea made as many marks as the Worms. 
Mr. Erneripee commented on the difficulty of interpreting these 
markings in the fieid, and said he quite agreed that the Annelida 
