' Fossil Organic Remains. 
23 
He considered each bed of secondary rock “as a sediment de- 
posited by an aqueous fluid and, exposing a system perfectly 
similar to that of Deluc, “ On the formation of valleys by longi- 
tudinal sinkings, and on the inclination of beds originally all 
horizontal,” he admits, with regard to Tuscany, in the manner 
of our modern geologists, “ six great epochs of nature ( sex dis- 
tinctce Etruria: facies , ex prasente facie Etruria collect a) ^ ac- 
cording as the sea periodically inundated the continent, or re- 
tired within its ancient limits.” In those times, when the obser- 
vation of nature gave rise in Italy to the first ideas regarding 
the relative age and succession of the primitive and secondary 
strata, zoology and geognosy could not yet be of mutual assist- 
ance, because the zoologists of those days were not acquainted 
with the rocks, and the geognosts were entirely strangers to the 
natural history of animals. Naturalists confined themselves to 
vague perceptions; they regarded as specifically identical all 
that presented any analogy of form ; but, at the same time, and 
this was a step made in the true road, they were attentive to 
the fossils found in such or such rocks. Hence the denomina- 
tions limestone with gryphites , limestone with trochites , slates 
with ferns , and slates with trilobites , (Gryphiten und Trochiten- 
Kalk, Krauter und Trilobiten-Schiefer), were long ago em- 
ployed by the mineralogists of Germany. The determination 
of genera whose characters are derived from the teeth, and 
other parts of the hinge, and from the opening of the shell, is 
much more difficult in the oldest secondary rocks than in the 
tertiary formations, the former being in general harder, and ad- 
hering more closely to the body of the shell. This difficulty 
increases, when it is attempted to distinguish the species ; it be- 
comes almost insurmountable in some limestone-rocks of the 
Transition class, and in the shell-limestone or muschelkalk, 
which contains broken shells. Could the zoological characters 
of a certain number of formations be taken from very distinct 
genera, and did the trilobites and orthoceratites belong exclu- 
sively to the transition formations, the gryphites to the alpine 
limestone (zechstein), the pectinites to the variegated sandstone 
or hunter sandstone (gres de Nebra), the trochites and mytilites 
to the shell-limestone (muschelkalk), the tellinae to the quader- 
sandstein, the ammonites and turritellae to the Jura limestone 
