430 
THE GEOLOGIST. 
organization — the last contains those of the lowest. The Avticulata 
and Mollusca are arranged side by side, as having something like an 
equality of pretension as regards their organization. The last class of 
either of these sub-kingdoms has no claim to be rankijd above the first 
class of the other. They cannot, therefore, be arranged in linear 
order. Of the Vertebrata, the mammals, the reptiles, and fishes 
abound ; the remains of birds, as might be expected, are more rare. Of 
the Articulata, crustaceans (now represented by crabs, lobsters, &c.) 
are in considerable numbers, comprising the various extinct genera of 
Trilobites which characterized some of the oldest formations. Among 
the Mollusca, the Cephalopoda (now feebly represented by the cuttle- 
fish, &c.) were formerly abundant, comprising large Orthoceratites and 
other similar forms, with the numerous genera of Ammonites, of which 
the general form will doubtless be familiar to most of our readers. 
Gasteropoda (univalves), and Lamellibranchiata and Brachiopoda 
(bivalves), arc exceedingly abundant, as might be expected, on account 
of the facility with which their shells would be preserved. Erachiopoda 
are especially abundant in the older formations. Also fossil Eadiaria, 
Polypi, and Infusoria abound. 
" The highest classes found in the Cambrian beds (as above defined), 
are Crustacea and Cephalopoda, with numerous fossils of lower classes. 
In the Silurian division, a few fishes appear, in addition to the lower 
classes of animals, of which, however, the species are for the most part 
changed. In the Devonian beds, fishes arc very abundant, and reptile- 
life also makes its appearance. In the coal-formation, plants first 
become abundant. The Lias abounds in enormous reptiles ; and in the 
Lower Oolites (Stonesfield slates) the first mammals* (small marsupial 
animals) appear. In the Tertiaries, large mammals abound, and 'finally 
Man was introduced. This recent introduction is proved by the fact of 
no human bones having been yet discovered in a fossilized state. Of 
all the species of animals now living, it is believed that none are found 
fossil, with the exception of a few in the most recent tertiary beds." 
The author's first proposition, then, is — ^Hhut the stralijicd leils were 
deposited fi-om water, and in the same manner as that in which we may 
so freqiiently observe earthy sediment to be deposited, after being held 
for a certain time in mechanical suspension in that element. If this 
deposition take place at a uniform rate, and the matter deposited be 
always of the same mineralogical eharactei', there will be no stratijication 
of the deposited mass ; but if the process be discontinuous, or the 
matter deposited should be at one time, for instance, argillaceous, and 
at another, arenaceous or calcareous, distinct beds superimposed on 
each other will be the necetsary consequence, and the mass will be 
stratified, as we actually observe the stratified portion of the earth's 
crust to be." 
The next proposition is, " that the matter which formed these leds, 
consisted of extremely fine sediment, very sloivly and gradually 
deposited, as shown by the preservation of delicate organic structures. 
Such beds are termed sedimentary, a term frequently also applied 
to the whole stratified mass, on account of the general pre- 
Still earlier, though very rare remains of small mammals, have been met with 
in the Triassic bccls of Germany aiiU Carolina. — Ed. Geologist, 
