116 FOSSILS THEIR NATURE AND ARRANGEMENT. 



Of course, all plants and animals are not preservable 

 alike, nor are the same organisms, though occurring in the 

 same formation, always found in the same state of preser- 

 vation. Plants and animals that have been exposed to 

 atmospheric decay before entombment will be less perfect 

 than those that have been suddenly and thoroughly im- 

 bedded. The harder parts of plants roots, stems, leathery- 

 leaves, and nut -like fruits will run a better chance of 

 preservation than the soft and succulent portions. Corals, 

 shells, crusts, bones, teeth, scutes, and scales, will be pre- 

 served when all the softer parts of the animals to which 

 they belong have entirely disappeared. The harder and 

 more massive portions of a skeleton will resist when the 

 softer and more slender have fallen to decay. The dense 

 and thoroughly ossified bones of an old animal will endure 

 where the spongy and unanchylosed members of a young 

 one fall asunder and perish. Ferns, mosses, and resinous 

 pines will resist maceration when other plants will totally 

 disappear. All things considered, aquatic animals run a 

 better chance of pre^ejcxatiQILthan terrestrial ones ; an3. the 

 bulkier land-mammals and amphibialfchan the birds and 

 insects. Gregarious animals, too, are likely to be found 

 in greater abundance than those living isolated and soli- 

 tary the catastrophe (earthquake, land-flood, or wind- 

 storm) which would destroy only a few of the latter, over- 

 whelming the former by hundreds of thousands. In this 

 way shoals of fishes may be suddenly suffocated by sub- 

 marine exhalations, shell-beds buried beneath obnoxious 

 sediments, herds of ruminants borne from the land by floods, 

 and clouds of insects swept into the sea by wind-storms. 

 The inconceivable numbers in which fossils are sometimes 

 found crowded into very limited areas would seem to point 

 to such accidents for their entombment their perfection, 



