Page - 357 - in The Origin of Species

APPEARANCE OF WHOLE GROUPS 357 lizard-like tail, bearing a pair of feathers on each joint, and with its wings furnished with two free claws, has been dis- covered in the oolitic slates of Solenhofcn. 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 extraordi- nary 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 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 com- mencement of the tertiary series. This was a sore trouble to me, adding as I then thought one more instance of the abrupt appearance 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 un- mistakeable 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 sub- family 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 palccontologists of the apparently sudden appearance of a whole group of species, is that of the teleostean fishes, low down, according to Agas- siz, in the Chalk period. This group includes the large ma- jority of existing species. But certain Jurassic and Triassic