Ancient Seas. 
1885.] 
481 
' th fils 5 P Iace > 11 ls not possible that foot-prints which 
1 st weie hollow could then be moulded in relief, and im- 
press themselves upon the lower surface of a stratum 
subsequently deposited over them, so that when separated 
obje<5t C ° U d PreSGnt b ° th SUrfaces of one and the sa me 
Secondly, mere tracks can display no detached portions 
behmg ° V ^ the Side ° f the b ° dy to whi <* the y 
Thiidly, it is not possible that the tracks of animals — 
walking leaping, or trailing parts of their bodies after them 
could display the fine delicate, sharply-marked and mani- 
o°ffer iamibCatl ° nS and mesdes wd ich a series of these plants 
Last y, fossils whose branching parts cross, intersect, and 
mutually cover each other must be true organisms, and not 
loot-marks, which if they meet may cross each other but 
cannot be deposited over each other. 
On these grounds M. de Saporta shows that the fossil 
Algae called in question by Nathorst and his followers are 
true vegetable remains, which may be accurately described 
and classified. 1 he author endeavours also to demonstrate 
the real existence of the “ problematical ” organisms which 
have but a remote resemblance to Algae. He shows, by an 
extensive series of instances, that petrifactions in half-relief 
are no uncommon phenomena in which only one side of 
vegetable parts generally the lower — is impressed and re- 
mains preserved. But if ancient land- or water-plants exist 
which aie fossilised in half-relief, the main objection to the 
vegetable nature of the contested structures falls to the 
ground, and it must be admitted that the half-reliefs may be 
plants. 1 hat such is really the case M. de Saporta shows 
from the materials which he has collected. He again ad- 
duces the inteilaced super-imposition of the impressions as 
a proof of the vegetable nature of the fossils. The foldings 
and intertwinings of the fossils and other spacial relations 
are opposed to every possibility of our having before us 
foot-prints. 
A minute and exhaustive study of the foot-prints of ani- 
mals is certainly of great interest, but M. de Saporta cautions 
us here against exaggerations. 
