Chap. X.] PAL^ONTOLOGICAL COLLECTIONS. 59 



several species of the Chthamalinse (a sub-family of 

 sessile cirripedes) coat the rocks all over the world in 

 infinite numbers : they are all strictly littoral, with the 

 exception of a single Mediterranean species, which 

 inhabits deep water, and this has been found fossil in 

 Sicily, whereas not one other species has hitherto been 

 found in any tertiary formation : yet it is known that 

 the genus Chthamalus existed during the Chalk period. 

 Lastly, many great deposits requiring a vast length of 

 time for their accumulation, are entirely destitute of 

 organic remains, without our being able to assign any 

 reason : one of the most striking instances is that of the 

 Flysch formation, which consists of shale and sandstone, 

 several thousand, occasionally even six thousand feet in 

 thickness, and extending for at least 300 miles from 

 Vienna to Switzerland; and although this great mass 

 has been most carefully searched, no fossils, except a 

 few vegetable remains, have been found. 



With respect to the terrestrial productions which lived 

 during the Secondary and Palaeozoic periods, it is super- 

 fluous to state that our evidence is fragmentary in an 

 extreme degree. For instance, until recently not a land- 

 shell was known belonging to either of these vast 

 periods, with the exception of one species discovered by 

 Sir C. Lyell and Dr. Dawson in the carboniferous strata 

 of North America ; but now land-shells have been found 

 in the lias. In regard to mammiferous remains, a 

 glance at the historical table published in Lyell's 

 Manual will bring home the truth, how accidental and 

 rare is their preservation, far better than pages of detail. 

 Nor is their rarity surprising, when we remember how 

 large a proportion of the bones of tertiary mammals 

 have been discovered either in caves or in lacustrine 



