336 SUDDEN APPEARANOE OF 



with, a long lizard-like tail, bearing a pair of feather? on 

 each joint, and with its wings furnished with two free 

 claws, has been discovered in the oolitic slates of Solenho- 

 fen. Hardly any recent discovery shows more forcibly 

 than this how little we as yet know of the former inhab- 

 itants 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 num- 

 ber of existing and extinct tertiary species; from the ex- 

 •traordinary abundance of the individuals of many species 

 all over the world, from the Arctic regions to the equator, 

 inhabiting various zones of depths, from tlie upper tidal 

 limits to fifty 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 discov- 

 ered 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 1 then thought, one more instance of the 

 abrupt appearance of a great group of species. But my 

 work had hardly been published, when a skillful pala3on- 

 togist, M. Bosquet, sent me a drawing of a perfect speci- 

 nien of an unmistakable 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 

 was a Chthamalus, a very common, large, and ubiquitous 

 genus, of which not one species has as yet been found even 

 in any tertiary stratum. Still more recently, a Pyrgoma, 

 a member of a distinct subfamily of sessile cirripedes, has 

 been discovered by Mr. Woodward in the upper chalk; so 

 that we now have abundant evidence of the existence of 

 this group of animals during the secondary period. 



The case most frequently insisted on by palaeontologists 

 of the apparently sudden appearance of a whole group of 

 species, is that of thet eleostean fishes, low down, according 

 to Agassiz, in the Chalk period. This group includes tlie 

 large majority of existing species. But certain Jurassic 



