258 PICTURESQUE SKETCHES 



same or different kind, without any long pause, and 

 often, it may be, while the preceding deposit was be- 

 coming solid ; but the new beds exhibit great local 

 differences and sometimes apparent repetition. One 

 thing, however, is perfectly clear in the midst of 

 all this change, introduction, and substitution of spe- 

 cies, namely, that there was on the whole no true 

 advance in the perfection or even the complication of 

 organic forms, between the commencement and the 

 close of the epoch ; for, at the outset, we find evi- 

 dence of the existence of reptiles of the two ex- 

 tremes of organization ; in the middle we have 

 merely a vast multiplication of reptilian species, ex- 

 hibiting very interesting and remarkable modifica- 

 tions, but no new type ; while towards the close 

 these all cease, and we revert to the same, or nearly 

 the same, modifications of lacertian structure as at 

 first. Neither in size, number, or affinity to higher 

 forms, nor, indeed, in any conceivable point, can we 

 trace systematic advance in organization in the rep- 

 tiles of this great saurian period. It must not be 

 forgotten also, that the reptiles were, with the excep- 

 tion of the few marsupial quadrupeds, the animals of 

 most complicated structure, and that they form, in 

 the strictest sense, the characteristic group of the 

 secondary period. 



Nor do we find any different result if we examine 

 the other groups. The birds exhibit indications of 

 their existence by a few footsteps in the new red 

 sandstone, at the commencement of the epoch, and 

 a very few isolated bones obtained from the chalk 

 give evidence of their presence scarcely more distinct 

 at its close. No such remains at all have yet been 



