166 BRITISH CICADM. 



marine origin did not preserve their remains. If we 

 have abmidant proof that beetles and other insects inha- 

 bited the shores of the lagoons and the river-swamps of 

 the coal-measm^es, we may well suppose their occm-rence 

 through the periods of the formations above, though 

 doubtless ranging under different genera and species. 



Fresh-water deposits are comparatively rare, and few 

 only are fitted to preserve the delicate organization of 

 insects. None but the finest sediments or volcanic 

 ashes seem to make a suitable matrix. We may 

 except, however, the resins of amber, gum-anime, 

 and copal. Kocks containing the iron oxides, as a 

 rule, are destructive to organisms ; thus the ferru- 

 ginous clays and sandstones are poor in examples. 

 Perhaps this may arise from the slow conversion of 

 the higher oxides of iron into the lower, and a simul- 

 taneous decomposition of carbon contained in animal 

 tissues. Calcareous muds and volcanic dusts are mostly 

 free from iron compounds, and they do not offer this 

 objection. 



The larger tracts of dry land in Oligocene, Miocene, 

 and Pliocene times were more favourable to the pre- 

 servation of insects, and it is here that we have 

 obtained our chief stores and representatives of ancient 

 Entomology. Such stores occur in the Tertiary strata 

 of Schambekn, CEningen, and Kadaboj, the quarries 

 of which have yielded numerous specimens to Prof. 

 Oswald Heer ; and the same occur also in those North- 

 American insect-beds of Florissant, which have become 

 famous through the labours of Mr.' S. Scudder. 



Our economic processes for the preservation of flesh, 

 fruit, and milk testify to the long unrecognized fact 

 that air, moisture, and organized germs are necessary 

 to cause fermentation and decay. The controlling 

 action of antiseptics and the influence of varied 

 temperature is now better known than formerly. It is 

 worthy of remark that wherever insectiferous beds 

 have been found, the individual remains are often 

 crowded within small spaces. 



