Chap. IX. GEOLOGICAL KECOED. 305 



stratum. Hence we now positively know that sessile 

 cirriped.es existed during the secondary period ; and 

 these cirripedes might have been the progenitors of our 

 many tertiary and existing species. 



The case most frequently insisted on by palaeonto- 

 logists of the apparently sudden appearance of a whole 

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

 down in the Chalk period. This group includes the 

 large majority of existing species. Lately, Professor 

 Pictet has carried their existence one sub-stage further 

 back ; and some palaeontologists believe that certain 

 much older fishes, of which the affinities are as yet im- 

 perfectly known, are really teleostean. Assuming, how- 

 ever, that the whole of them did appear, as Agassiz 

 believes, at the commencement of the chalk formation, 

 the fact would certainly be highly remarkable ; but I 

 cannot see that it would be an insuperable difficulty on 

 my theory, unless it could likewise be shown that the 

 species of this group appeared suddenly and simul- 

 taneously throughout the world at this same period. It 

 is almost superfluous to remark that hardly any fossil- 

 fish are known from south of the equator; and by 

 running through Pictet's Palaeontology it will be seen 

 that very few species are known from several formations 

 in Europe. Some few families of fish now have a 

 confined range; the teleostean fish might formerly 

 have had a similarly confined range, and after having 

 been largely developed in some one sea, might have 

 spread widely. Nor have we any right to suppose that 

 the seas of the world have always been so freely open 

 from south to north as they are at present. Even at 

 this day, if the Malay Archipelago were converted into 

 land, the tropical parts of the Indian Ocean would form 

 a large and perfectly enclosed basin, in which any great 

 group of marine animals might be multiplied ; and 



