80 SUDDEN APPEARANCE OP [Chap. X. 



deposition of the upper greensand; 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 

 species ; from the extraordinary abundance of the in- 

 dividuals 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 recognised ; from all 

 these circumstances, I inferred that, had sessile cii'ripedes 

 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 

 tliis 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 mor» instance of the abrupt ap- 

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

 hardly been published, when a skiKul palaeontologist, 

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

 of an unmistakeable sessile cirripede, which he had 

 himself extracted from the chalk of Belgium. And, as 

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



