164 Physical Geography. 



first described them, the ' insect limestones.' The 

 fossilised contents of these bands throw some light on 

 the physical geography of the lands that bordered the 

 waters of the time, for in them have been found 

 numerous elytra and other remains of Beetles, Grass- 

 hoppers, Cicadas, Dragon-flies, and other neuropterous 

 insects, associated with a fresh-water shell of the genus 

 Cyclas, the shells of Cypris, and with ferns, Cycads, 

 and leaves of Monocotyledonous plants. These beds, 

 therefore, indicate either fresh-water strata, or else the 

 immediate proximity of land, from whence streams 

 washed into the sea insects, fresh-water Crustacea, 

 shells, and land plants. 



Sir Charles Lyell remarks that 'the size of the 

 species (of insects) is usually small, and such as taken 

 alone would imply a temperate climate ; but many 

 of the associated remains of other classes must lead 

 to a different conclusion.' 1 This, however, seems to 

 be explained by a remark long ago made to me by 

 Edward Forbes, who, while working with Captain 

 Graves, during the hydrographical survey of the ^Egean 

 Sea, observed that, during heavy rains, vast numbers 

 of insects were washed into the sea, not such as in- 

 habited the low hot shores of the ^Egean, but those 

 that lived in the high cool regions of the neighbouring 

 mountains, which, caught in the floods of rain, were 

 washed into rivers and borne onwards to yield food for 

 fishes in the ocean. 



In conclusion, if, as I believe, the New Ked Marl 

 was deposited in a salt lake, if it be the equivalent in 

 time of the marine Infra-Lias beds of Stoppani in 

 Italy, and of the Lower St. Cassian and Hallstatt beds 

 of Hauer and Suess, then the Avicula contorta beds, 

 1 Student's Elements of Geology,' p. 351, 1874. 



