430 Darwin, and after Darwin, 



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

 of the preservation of footsteps in the new red sandstone of the 

 United States, who would have ventured to suppose that, no 

 less than at least thirty kinds of bird-like animals, some of 

 gigantic size, existed during that period ? Not a fragment 

 of bone has been discovered in these beds. Not long ago 

 palaeontologists maintained that the whole class of birds came 

 suddenly into existence during the eocene period ; but now 

 we know, on the authority of Professor Owen, that a bird 

 certainly lived during the deposition of the upper green-sand. 

 And still more recently that strange bird, the Archeopteryx . . . 

 has been discovered in the oolitic slates of Solenhofen. Hardly 

 any recent discovery shows more forcibly than this, how little 

 we as yet know of the former inhabitants of the world. 



I may give another instance, which, from having passed 

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

 Fossil Sessile Cirripedes, I stated that, from the number of 

 existing and extinct tertiary species ; from the extraordinary 

 abundance of the individuals of many species all over the world 

 from the Arctic regions to the equator, inhabiting various 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 ease with which even a fragment of 

 a valve can be recognized ; from all these circumstances, I 

 inferred that had sessile cirripedes existed during the secondary 

 periods, they would certainly have been preserved and dis- 

 covered ; and as not one species had then been discovered 

 in beds of this age, I concluded that this great group had been 

 suddenly developed at the commencement of the tertiary series. 

 This was a sore trouble to me, adding as I thought one more 

 instance of the abrupt appearance of a great group of species. 

 But my work had hardly been published, when a skilful palaeon- 

 tologist, M. Bosquet, sent me a drawing of a perfect specimen of 

 an unmistakeable sessile cirripede, which he had himself ex- 

 tracted from the chalk of Belgium. And, as if to make the case 

 as striking as possible, this sessile cirripede was a Chthamalus, 

 a very common, large, and ubiquitous genus, of which not one 

 specimen has as yet been found even in any tertiary stratum. 

 Still more recently, a Pyrgoma, a member of a distinct sub- 



