IMPERFECTION OF GEOLOGICAL RECORD 87 



a skilful paleontologist, M. Bosquet, sent me a drawing 

 of a perfect specimen of an unmistakable sessile cirri ped, 

 which he had himself extracted from the chalk of Bel- 

 gium. And, as if to make the case as striking as pos- 

 sible, this cirriped 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 cirripeds, 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 paleontol- 

 ogists of the apparently sudden appearance of a whole 

 group of species, is that of the teleostean fishes, low 

 down, according to Agassiz, in the Chalk period. This 

 group includes the large majority of existing species. 

 But certain Jurassic and Triassic forms are now com- 

 monly admitted to be teleostean; and even some paleo- 

 zoic forms have thus been classed by one high authority. 

 If the teleosteans had really appeared suddenly in the 

 northern hemisphere at the commencement of the chalk 

 formation, the fact would have been highly remarkable; 

 but it would not have formed an insuperable difficulty, 

 unless it could likewise have been shown that at the 

 same period the species were suddenly and simultane- 

 ously developed in other quarters of the world. It is 

 almost superfluous to remark that hardly any fossil-fish 

 are known from south of the equator; and by running 

 through Pictet's Paleontology it will be seen that very 

 few species are known from several formations in Eu- 

 rope. Some few families of fish now have a confined 



— Science — 21 



