430 



THE GEOLOGIST. 



oro-anization — the last contains those of the lowest. The Articiilata 

 and Mollusca are arranged side by side, as having somctliing- like an 

 equality of pretension as regards their organization. The last class of 

 either of these sub-kingdoms has no claim to be ranked above the first 

 class of the other. They cannot, therefore, be arranged in linear 

 order. Of the Yertebrata, 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 Erachiopoda 

 (bivalves), are exceedingly abundant, as might bo expected, on account 

 of the facility with which their shells would be preserved. JBrachiopoda 

 are especially abundant in the older formations. Also fossil Kadiaria, 

 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 are 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 — '' tluit the stratified leds were 

 deposited from water, and in the same manner as that in which we may 

 so frequently 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 character, there will be no stratification 

 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 necessary 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, tliat 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 beds of Germany and Carolina.— Ed. Geologist. 



