80 SUDDEN APPEARANCE OF [Chap. X. 



the deposition of the upper greensandj and still more 

 recently, that strange bird, the Archeopteryx, with a 

 long lizard-like tail, bearing a pair of feathers on each 

 joint, and with its wings furnished with two free claws, 

 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 large number of existing and extinct tertiary spe- 

 cies; from the extraordinary abundance of the indi- 

 viduals 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 pre- 

 served in the oldest tertiary beds; from the ease with 

 which evena fragment of avalve can be recognised; from 

 all these circumstances, I inferred that, had sessile cirri- 

 pedes existed during the secondary periods, they would 

 certainly have been preserved and discovered; 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 ter- 

 tiary series. This was a sore trouble to me, adding as 

 I then thought one more instance of the abrupt ap- 

 pearance of a great group of species. But my work had 

 hardly been published, when a skilful palaeontologist, 

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

 of an unmistakable sessile cirripede, which he had him- 

 self extracted from the chalk of Belgium. And, as 

 if to make the case as striking as possible, this cirripede 



