288 SUDDEN AITEAEANCE OF Cuap. IX. 



on the first appearance and disappearance of several groups 

 of animals have l)ocn considerably modified ; and a third 

 edition •would rociuire still further changes. I may recall 

 the ■well-known fact that in geological treatises, published 

 not many years ago, mammals were always spoken of as 

 liaving abruptly come in at the commencement of the tertiary 

 series. And now one of the richest known accumulations of 

 fossil mammals, for its thickness, belongs to the middle of 

 the secondary series ; and true mammals have been discov- 

 ered in the new red sandstone at nearly the commencement of 

 tliis great series. Cuvier used to urge that no monkey oc- 

 curred in any tertiary stratum ; but now extinct species have 

 been discovered in India, South America, and in Europe, as far 

 back as the miocene stage. Had it not been for the rare acci- 

 dent of the preservation of footsteps in the new red sandstone 

 of the United States, who would have A^entured to suppose 

 that, besides reptiles, no less than at least thirty kinds of birds, 

 some of gigantic size, existed during that period ? Not a frag- 

 ment of bone has been discovered in these beds. Notwith- 

 standing that the number of joints shown in the fossil impres- 

 sions corresponds with the number in the several toes of living 

 birds' feet, some authors doubt whether the animals which left 

 these impressions were really birds. Until quite recently these 

 authors might have maintained, and some have maintained, that 

 the whole class of birds came suddenly into existence during 

 the eocene period; but now we know, on the authority of 

 Prof. Owen, that a bird certainly lived during the deposition 

 of the upper greensand ; and still more recently, that strange 

 bird, the ArchcopterA'x, with a long, lizard-like tail, bearing a 

 pair of feathers on each joint, and with its wings furnished with 

 two free claAvs, has been discovered in the oolitic slates of So- 

 Icnhofcn. Hardly any recent discovery shows more forcibly 

 than this, how little we as yet know of the former inhabitants 

 of the Avorld. 



I may give another instance, which, from having passed im- 

 der my own eyes, has much struck me. In a memoir on Fossil 

 Sessile Cirripedes, I have stated that, from the large number 

 of existing and extinct tertiary species ; from the extraordinary 

 abundance of the individuals of many sj:)ecies all over the world, 

 from the Arctic regions to the equator, inhabiting A-arious 

 zones of depths from the upper tidal limits to 50 fathoms ; from 

 the perfect manner in which specimens are preserved in the 

 oldest tertiary beds ; from the case with which even a frag- 



